Linux_Networking_HOWTO
Joshua Drake
Copyright © 2000 Commandprompt, Inc
v1.7.0, 29 December 2000
This is a LinuxPorts.Com Document for the Linux Documentation Project. It has
been sponsored in part by the Open_Source_Documentation_Fund.
The current version is v1.7.0 is a minor update with some grammar fixes.
-------------------------------------------------------------------------------
Table of Contents
1. How_can_I_help?
1.1. Assisting_with_the_Net-HOWTO
2. Document_History
2.1. Feedback
3. How_to_use_this_HOWTO.
3.1. Conventions_used_in_this_document
4. General_Information_about_Linux_Networking.
4.1. Linux_Networking_Resources.
4.2. Sources_of_non-linux-specific_network_information.
5. Generic_Network_Configuration_Information.
5.1. What_do_I_need_to_start_?
5.2. Where_should_I_put_the_configuration_commands_?
5.3. Creating_your_network_interfaces.
5.4. Configuring_a_network_interface._Kernels_2.0_and_2.2
5.5. Configuring_your_Name_Resolver.
5.6. Configuring_your_loopback_interface.
5.7. Routing.
5.8. Configuring_your_network_servers_and_services.
5.9. Other_miscellaneous_network_related_configuration_files.
5.10. Network_Security_and_access_control.
6. Ethernet_Information
6.1. Supported_Ethernet_Cards
6.2. General_Ethernet_Information
6.3. Using_2_or_more_Ethernet_Cards_in_the_same_machine
7. IP_Related_Information
7.1. Kernel_Level_Options
7.2. EQL_-_multiple_line_traffic_equaliser
7.3. IP_Accounting_(for_Linux-2.0)
7.4. IP_Aliasing
7.5. IP_Firewall_(for_Linux-2.0)
7.6. IPIP_Encapsulation
7.7. IP_Masquerade
7.8. IP_Transparent_Proxy
7.9. IPv6
7.10. IPv6_Linux_resources
7.11. Mobile_IP
7.12. Multicast
7.13. Traffic_Shaper_-_Changing_allowed_bandwidth
8. DHCP_and_DHCPD
8.1. DHCP_Client_Setup_for_users_of_LinuxConf
8.2. DHCP_Server_Setup_for_Linux
9. Advanced_Networking_with_Kernel_2.2
9.1. The_Basics
9.2. Adding_a_route_with_the_new_ip_tools
9.3. Using_NAT_with_Kernel_2.2
10. Kernel_2.2_IP_Command_Reference_(Work_In_Progress)
10.1. ip
11. Using_common_PC_hardware
11.1. ISDN
11.2. PLIP_for_Linux-2.0
11.3. PPP
11.4. SLIP_client_-_(Antiquated)
12. Other_Network_Technologies
12.1. ARCNet
12.2. Appletalk_(AF_APPLETALK)
12.3. ATM
12.4. AX25_(AF_AX25)
12.5. DECNet
12.6. FDDI
12.7. Frame_Relay
12.8. IPX_(AF_IPX)
12.9. NetRom_(AF_NETROM)
12.10. Rose_protocol_(AF_ROSE)
12.11. SAMBA_-_`NetBEUI',_`NetBios',_`CIFS'_support.
12.12. STRIP_support_(Starmode_Radio_IP)
12.13. Token_Ring
12.14. X.25
12.15. WaveLan_Card
13. Cables_and_Cabling
13.1. Serial_NULL_Modem_cable
13.2. Parallel_port_cable_(PLIP_cable)
13.3. 10base2_(thin_coax)_Ethernet_Cabling
13.4. Twisted_Pair_Ethernet_Cable
14. Glossary_of_Terms_used_in_this_document.
15. Authors
15.1. Current
15.2. Past
16. Copyright.
-------------------------------------------------------------------------------
Chapter 1. How can I help?
We will try to provide comprehensive coverage for all Linux Networking
implementations. However, time is of the essence, and this document is not a
revenue maker. We provide this information in the hope that it will be useful
to both the Linux Community and to newly converted Linux users. We are always
interested in feedback! We will implement every relevant topic possible in this
HOWTO document.
-------------------------------------------------------------------------------
1.1. Assisting with the Net-HOWTO
If you would like to assist with this document, there are two primary avenues
that are extremely helpful.
* Purchase_an_OpenBook! If you purchase OpenDocs books, OpenDocs Publishing
will donate a portion of the proceeds back to the Open_Source_Documentation
Fund. This fund assists authors financially while they continue to write
documentation for Open Source projects.
* Provide a monetary contribution to the document. By contributing, you can
even request what you would like to have updated, written, or expanded within
the document. To provide a monetary contribution, please contact Command
Prompt,_Inc. You may also contact Joshua_Drake.
* If you have written something that you would like to contribute, please email
it to poet@linuxports.com
-------------------------------------------------------------------------------
Chapter 2. Document History
The original NET-FAQ was written by Matt Welsh and Terry Dawson. NET-FAQ
answered frequently asked questions about networking for Linux (at a time
before the Linux Documentation Project had formally started). This document
covered the very early development versions of the Linux Networking Kernel. The
NET-2-HOWTO superseded the NET-FAQ, and it was one of the original LDP HOWTO
documents. It covered what was called "version 2" (and subsequently "version
3") of the Linux kernel Networking software. NET-2_HOWTO in turn superseded it,
and relates only to version 4 of the Linux Networking Kernel (ie: kernel
releases 2.x and 2.2.x. ).
Previous versions of this document became quite large because of the enormous
amount of material that fell within its scope. To help reduce this problem, a
number of HOWTOs dealing with specific networking topics have been produced.
This document will provide pointers to them where relevant, and it will cover
those areas not yet reviewed by other documents.
-------------------------------------------------------------------------------
2.1. Feedback
We are always interested in feedback. Please contact us at:
poet@linuxports.com.
If you find anything erroneous, or if you feel that something should be added,
please contact_us.
Was_this_section_helpful?_Why_not_Donate_$2.50?
-------------------------------------------------------------------------------
Chapter 3. How to use this HOWTO.
This document is organized top-down. The first sections include informative
material, and it can be skipped if you are not interested; what follows is a
generic discussion of networking issues, and you must ensure you understand
this before proceeding to more specific parts. The ``technology specific''
information is grouped into three main sections: Ethernet and IP-related
information, technologies pertaining to widespread PC hardware, and seldom-used
technologies.
The suggested path through this document is as follows:
Read the generic sections:
These sections apply to almost every technology described in subsequent
sections, and they are very important for you to understand. I expect
many of the readers will be confident with this material.
Consider your network:
You should know how your network is (or will be) designed, and you should
also be familiar with exactly what hardware and technology types you will
be implementing.
If you are directly connected to a LAN or the Internet, please refer to the
``Ethernet and IP'' section:
This section describes basic Ethernet configurations, and it describes
the various features that Linux offers for IP networking (ie:
firewalling, advanced routing, etc).
If you are interested in low-cost local networks or dial-up connections,
please refer to the next section
This section describes the widespread technologies used on personal
workstations (ie: PLIP, PPP, SLIP, and ISDN).
Please refer to the technology-specific sections that are related to your
requirements:
Your needs may differ from IP and/or other common hardware This final
section covers details specific to both non-IP protocols and to peculiar
communication hardware.
Do the configuration work:
You should actually try to configure your network. Take careful note of
any existing problems
Look for further help:
If you experience problems that this document does not help you to
resolve, then you should refer to the sections related to "Help" and
"Where to report bugs".
Have fun!
Networking is fun! Enjoy it!
-------------------------------------------------------------------------------
3.1. Conventions used in this document
No special conventions are used here, but you must be warned about the way
commands are shown. This howto follows the classic Unix documentation: any
command you type to your shell is prefixed by a prompt. It shows "user%" as the
prompt for commands that do not require superuser privileges, and "root#" as
the prompt for commands that need to run as root. I chose to use "root#"
instead of a plain "#" to prevent confusion with snapshots from shell scripts
(where the hash mark is used to define comment lines).
When ``Kernel Compile Options'' are shown, they are represented in the format
used by menuconfig. They should be understandable even if you (like me) are not
used to menuconfig. If you are in doubt about the options' nesting, then
running the program once can always help. Was_this_section_helpful?_Why_not
Donate_$2.50?
-------------------------------------------------------------------------------
Chapter 4. General Information about Linux Networking.
4.1. Linux Networking Resources.
There are a number of places where you can find good information about Linux
networking.
There are a wealth of Consultants available to assist you. A search able
listing can be found at: http://www.linuxports.com/.
Alan Cox, the current maintainer of the Linux kernel networking code, maintains
a world wide web page containing highlights of current and new developments in
Linux Networking: www.uk.linux.org.
There is a newsgroup in the Linux news hierarchy dedicated to networking and
related matters at this location: comp.os.linux.networking
You can also subscribe to a mailing list where you may ask questions relating
to Linux networking. Send an email message for a subscription to:
______________________________
|To: majordomo@vger.rutgers.edu|
| Subject: anything at all |
| Message: |
| subscribe_linux-net__________|
Please remember to include as much relevant detail about the problem as
possible. You should specify the versions of software that you are using
(especially the kernel version), the version of tools such as pppd/ or dip ,
and the exact nature of the problem(s) that you are experiencing. This means
you should take notes of both the exact syntax of error message(s) you receive,
and of any commands that you are issuing. Was_this_section_helpful?_Why_not
Donate_$2.50?
-------------------------------------------------------------------------------
4.2. Sources of non-linux-specific network information.
If you are after some basic tutorial information on tcp/ip networking, then I
recommend you take a look at the following documents:
tcp/ip introduction:
This document comes as both a text_version and a postscript_version.
tcp/ip administration:
This document comes as both a text_version and a postscript_version.
If you are after some more detailed information on tcp/ip networking, then I
highly recommend:
"Inter networking with TCP/IP, Volume 1: Principles, Protocols and
Architecture, by Douglas E. Comer, ISBN 0-13-227836-7, Prentice Hall
publications, Third Edition, 1995."
If you are wanting to learn about how to write network applications in a Unix
compatible environment, then I recommend:
"Unix Network Programming, by W. Richard Stevens, ISBN 0-13-949876-1, Prentice
Hall Publications, 1990."
A second edition of this book is appearing on the bookshelves. The new book is
made up of three volumes. Check Prenice-Hall's_web_site for further details.
You might also try the comp.protocols.tcp-ip newsgroup.
RFCs are an important source of specific technical information relating to the
Internet and the tcp/ip suite of protocols. RFC is an acronym for `Request For
Comment' and it is the standard means of submitting and documenting Internet
protocol standards. There are many RFC repositories. Many of these sites are
ftp sites. Others provide World Wide Web access (with an associated search
engine) that allows you to search the RFC database for particular keywords.
One possible source for RFCs is at Nexor_RFC_database. Was_this_section
helpful?_Why_not_Donate_$2.50?
-------------------------------------------------------------------------------
Chapter 5. Generic Network Configuration Information.
You will pretty much need to know and understand the following subsections
before you actually try to configure your network. They are fundamental
principles that apply regardless of the exact nature of the network you wish to
deploy.
-------------------------------------------------------------------------------
5.1. What do I need to start ?
Before you start building or configuring your network, you will need certain
items. The most important of these are:
-------------------------------------------------------------------------------
5.1.1. Current Kernel source(Optional).
Please note:
The majority of current distributions come with networking enabled. It may not
be required to recompile the kernel. If you are running well known hardware you
should be fine. For example: 3COM NIC, NE2000 NIC, or an Intel NIC. However, if
you find yourself in the position that you do need to update the kernel, the
following information is provided.
Because the kernel you are running now might not yet have support for the
network types or cards that you wish to use, you will probably need the kernel
source to recompile the kernel with the appropriate options.
For users of the major distributions such as Redhat, Caldera, Debian, or Suse,
this no longer holds true. As long as you stay within the mainstream of
hardware, there should be no need to recompile your kernel (unless there is a
very specific feature that you need).
You can always obtain the latest kernel source from ftp.cdrom.com. This is not
the official site, but they have LOTS of bandwidth and capacity. The official
site is kernel.org, however, please use the above URL if you can. Please
remember that ftp.kernel.org is seriously overloaded. Use a mirror.
Normally the kernel source will be untarred into the /usr/src/linux directory.
For information on how to apply patches and build the kernel, you should read
the Kernel-HOWTO. For information on how to configure kernel modules, you
should read the ``Modules mini-HOWTO''. The README file found in the kernel
sources and the Documentation directory are very informative: for the brave
reader!
Unless specifically stated, I recommend you stick with the standard kernel
release (the one with the even number as the second digit in the version
number). Development release kernels (the ones with the odd second digit) may
have structural or other changes that may cause problems working with other
software on your system. If you are uncertain that you could resolve those
sorts of problems, then don't use Development release kernels.
-------------------------------------------------------------------------------
5.1.2. IP Addresses: an Explanation.
Internet Protocol Addresses are composed of four bytes. The convention is to
write addresses in what is called `dotted decimal notation'. In this form, each
byte is converted to a decimal number, (0-255). It drops any leading zeros
(unless the number is zero) and written with each byte separated by a `.'
character. By convention, each interface of a host or router has an IP address.
It is legal for the same IP address to be used on each interface of a single
machine, but usually each interface will have its own address.
Internet Protocol Networks are contiguous sequences of IP addresses. All
addresses within a network have a number of digits within the address in
common. The portion of the address that is common amongst all addresses within
the network is called the `network portion' of the address. The remaining
digits are called the `host portion'. The number of bits that are shared by all
addresses within a network is called the netmask. It is the role of the netmask
to determine which addresses belong to the network it is applied to and which
don't belong. For example, consider the following:
___________________________________
|----------------- --------------- |
| Host Address 192.168.110.23 |
| Network Mask 255.255.255.0 |
| Network Portion 192.168.110. |
| Host portion .23 |
| ----------------- ---------------|
| Network Address 192.168.110.0 |
| Broadcast Address 192.168.110.255|
| -----------------__---------------|
Any address that is 'bitwise anded' with its netmask will reveal the address of
the network that it belongs to. The network address is therefore always the
lowest numbered address within the range of addresses on the network, and it
always has the host portion of the address coded in all zeroes.
The broadcast address is a special address that every host on the network
listens to (in addition to its own unique address). This address is the one
that datagrams are sent to if every host on the network is meant to receive it.
Certain types of data, like routing information and warning messages, are
transmitted to the broadcast address so that every host on the network can
receive it simultaneously. There are two commonly used standards for the
broadcast address. The most widely accepted one is to use the highest possible
address on the network as the broadcast address. In the above example, this
would be 192.168.110.255. For some reason other sites have adopted the
convention of using the network address as the broadcast address. In practice
it doesn't matter very much which you use, but you must make sure that every
host on the network is configured with the same broadcast address.
For administrative reasons (some time early in the development of the IP
protocol), some arbitrary groups of addresses were formed into networks. These
networks were grouped into what are called classes. Classes provide a number of
standard size networks that could be allocated. The ranges allocated are:
_____________________________________________________________________________
|-----------------------------------------------------------------------------|
|--- |
| | Network | Netmask | Network Addresses | |
| | Class | | | |
| ----------------------------------------------------------------------------|
|---- |
| | A | 255.0.0.0 | 0.0.0.0 - 127.255.255.255 | |
| | B | 255.255.0.0 | 128.0.0.0 - 191.255.255.255 | |
| | C | 255.255.255.0 | 192.0.0.0 - 223.255.255.255 | |
| |Multicast| 240.0.0.0 | 224.0.0.0 - 239.255.255.255 | |
| ----------------------------------------------------------------------------|
|----_________________________________________________________________________|
What addresses you should use depends on exactly what it is that you are doing.
You may have to use a combination of the following activities to get all the
addresses you need:
Building a brand new network that will never connect to the Internet
If you are building a private network, and you never intend that network
to be connected to the Internet, then you can choose whatever addresses
you like. However, for safety and consistency reasons, there have been
some IP network addresses that have been reserved specifically for this
purpose. These are specified in RFC1597 and are as follows:
____________________________________________________________
|----------------------------------------------------------- |
| | RESERVED PRIVATE NETWORK ALLOCATIONS ||
| -----------------------------------------------------------|
| | Network | Netmask | Network Addresses ||
| | Class | | ||
| -----------------------------------------------------------|
| | A | 255.0.0.0 | 10.0.0.0 - 10.255.255.255 ||
| | B | 255.255.0.0 | 172.16.0.0 - 172.31.255.255 ||
| | C | 255.255.255.0 | 192.168.0.0 - 192.168.255.255 ||
| -----------------------------------------------------------|
You should first decide how large you want your network to be, then
choose as many of the addresses as you require.
-------------------------------------------------------------------------------
5.2. Where should I put the configuration commands ?
There are a few different approaches to Linux system boot procedures. After the
kernel boots, it always executes a program called `init'. The init program then
reads its configuration file called /etc/inittab and commences the boot
process. There are a few different flavors of init Everyone now seems to be
gravitating to the System V (Five) flavor, developed by Miguel van Smoorenburg.
Despite the fact that the init program is always the same, the setup of system
boot is organized in a different way by each distribution.
Usually the /etc/inittab file contains an entry looking something like:
____________________________
|si::sysinit:/etc/init.d/boot|
This line specifies the name of the shell script file that actually manages the
boot sequence. This file is somewhat equivalent to the AUTOEXEC.BAT file in MS-
DOS.
There are usually other scripts that are called by the boot script, and often
the network is configured within one of these scripts.
The following table may be used as a guide for your system:
_____________________________________________________________________________
| |
| ---------------------------------------------------------------------------|
| Distrib. | Interface Config/Routing | Server Initialization |
| ---------------------------------------------------------------------------|
| Debian | /etc/init.d/network | /etc/rc2.d/* |
| ---------------------------------------------------------------------------|
| Slackware| /etc/rc.d/rc.inet1 | /etc/rc.d/rc.inet2 |
| ---------------------------------------------------------------------------|
| RedHat | /etc/rc.d/init.d/network | /etc/rc.d/rc3.d/* |
| ---------------------------------------------------------------------------|
|_____________________________________________________________________________|
Note that Debian and Red Hat use a whole directory to host scripts that fire up
system services (and usually information does not lie within these files: for
example, Red Hat systems store all of system configuration in files under /etc/
sysconfig, where it is retrieved by boot scripts). If you want to grasp the
details of the boot process, my suggestion is to check /etc/inittab and the
documentation that accompanies init. Linux Journal is also going to publish an
article about system initialization, and this document will point to it as soon
as it is available on the web.
Most modern distributions include a program that will allow you to configure
many of the common sorts of network interfaces. If you have one of these, you
should see if it will do what you want before attempting a manual
configuration.
__________________________________________
|----------------------------------------- |
| Distrib | Network configuration program|
| -----------------------------------------|
| RedHat | /usr/bin/netcfg |
| Slackware | /sbin/netconfig |
| -----------------------------------------|
Was_this_section_helpful?_Why_not_Donate_$2.50?
-------------------------------------------------------------------------------
5.3. Creating your network interfaces.
In many Unix operating systems, the network devices have appearances in the /
dev directory. This is not so in Linux. In Linux, the network devices are
created dynamically in software, and they do not require device files to be
present.
In the majority of cases, the network device is automatically created by the
device driver (while it is initializing and locating your hardware). For
example, the Ethernet device driver creates eth[0..n] interfaces sequentially
as it locates your Ethernet hardware. The first Ethernet card found becomes
eth0, the second eth1 etc.
In some cases though, notably with slip and ppp, the network devices are
created through the action of some user program. The same sequential device
numbering applies, but the devices are not created automatically at boot time.
The reason for this is that unlike Ethernet devices, the number of active slip
or ppp devices may vary during the uptime of the machine. These cases will be
covered in more detail in later sections. Was_this_section_helpful?_Why_not
Donate_$2.50?
-------------------------------------------------------------------------------
5.4. Configuring a network interface. Kernels 2.0 and 2.2
When you have all of the programs you need (and your address and network
information), you can configure your network interfaces. When we talk about
configuring a network interface, we are talking about two items. One is the
process of assigning appropriate addresses to a network device. The second is
setting the appropriate values for other configurable parameters of a network
device. The program most commonly used to do this is the ifconfig (interface
configure) command.
Typically you would use a command similar to the following:
________________________________________________________
|root#_ifconfig_eth0_192.168.0.1_netmask_255.255.255.0_up|
In this example, I'm configuring an Ethernet interface `eth0' with the IP
address `192.168.0.1' and a network mask of `255.255.255.0'. The `up' that
trails the command tells the interface that it should become active (but can
usually be omitted) since it is the default. To shutdown an interface, you can
just call ``ifconfig eth0 down''.
The kernel assumes certain defaults when you are configuring interfaces. For
example, you may specify the network address and broadcast address for an
interface. If you don't (as in my example above), then the kernel will make
reasonable guesses as to what these addresses should be. If you don't supply a
netmask then on the network class of the IP address is auto-configured. In my
example, the kernel would assume that it is a class-C network that is being
configured on the interface. It would thus configure a network address of
`192.168.0.0' ,and a broadcast address of `192.168.0.255' for the interface.
There are many other options to the ifconfig command. The most important of
these are:
up
This option activates an interface (and it is the default).
down
This option deactivates an interface.
[-]arp
This option enables or disables use of the address resolution protocol on
this interface .
[-]allmulti
This option enables or disables the reception of all hardware multicast
packets. Hardware multicast enables groups of hosts to receive packets
addressed to special destinations. This may be of importance if you are
using applications like desktop video conferencing. This option is
normally not used.
mtu N
This parameter allows you to set the MTU of this device.
netmask <addr>
This parameter allows you to set the network mask of the network. This
device belongs to:
irq <addr>
This parameter only works on certain types of hardware. It allows you to
set the hardware IRQ of this device.
[-]broadcast [addr]
This parameter allows you to enable and set the accepting of datagrams
destined to the broadcast address.It also allows you to disable reception
of these datagrams.
[-]pointopoint [addr]
This parameter allows you to set the address of the machine at the remote
end of a Point-to-Point link (ie; for slip or ppp).
hw <type <addr>
This parameter allows you to set the hardware address of certain types of
network devices. This is not often useful for Ethernet, but is useful for
other network types like AX.25.
With the release of Kernel 2.2, there are a number of options available that
are not listed above. Some of the most interesting ones are tunneling and IPV6.
The ifconfig parameters for kernel 2.2 are listed below.
interface
The name of the interface. This is usually a driver name followed by a
unit number. For example, eth0 for the first Ethernet interface.
up
This flag causes the interface to be activated. It is implicitly
specified if an address is assigned to the interface.
down
This flag causes the driver for this interface to be shut down.
[-]arp
Enables or disables the use of the ARP protocol on this interface.
[-]promisc
Enables or disables the promiscuous mode of the interface. If selected,
all packets on the network will be received by the interface.
[-]allmulti
Enables or disables all-multicast mode. If selected, all multicast
packets on the network will be received by the interface.
metric N
This parameter sets the interface metric.
mtu N
This parameter sets the Maximum Transfer Unit (MTU) of an interface.
dstaddr addr
Sets the remote IP address for a point-to-point link (such as PPP). This
keyword is now obsolete; you should now use the pointopoint keyword.
netmask addr
Sets the IP network mask for this interface. This value defaults to the
usual class A, B or C network mask (as derived from the interface IP
address). It can, however, be set to any value.
add addr prefixlen
Adds an IPv6 address to an interface.
del addr prefixlen
Removes an IPv6 address from an interface.
tunnel aa.bb.cc.dd
Creates a new SIT (IPv6-in-IPv4) device that tunnels to the given
destination.
irq addr
Sets the interrupt line used by this device. Not all devices can
dynamically change their IRQ set- ting.
io_addr addr
Sets the start address in I/O space for this device.
mem_start addr
Set the start address for shared memory used by this device. Only a few
devices need this parameter.
media type
Sets the physical port (or medium type) to be used by the device. Not all
devices can change this set- ting. Those that can change the setting vary
in what values they support. Typical values for type are 10base2 (thin
Ethernet), 10baseT (twisted-pair 10Mbps Ethernet), AUI (external
transceiver) and so on. The special medium type of auto can be used to
tell the driver to auto-sense the media. Again, not all drivers can do
this.
[-]broadcast [addr]
If the address argument is given, set the protocol broadcast address for
this interface. Otherwise, set (or clear) the IFF_BROADCAST flag for the
interface.
[-]pointopoint [addr]
This keyword enables the point-to-point mode of an interface. This means
that it is a direct link between two machines, and that nobody else is
listening on it. If the address argument is also given, set the pro-
tocol address of the other side of the link ( just as the obsolete
dstaddr keyword does). Otherwise, set or clear the IFF_POINTOPOINT flag
for the interface.
hw class address
Set the hardware address of this interface (if the device driver supports
this operation). The keyword must be followed by the name of the hardware
class and the printable ASCII equivalent of the hardware address.
Hardware classes currently supported include ether (Ethernet), ax25 (AMPR
AX.25), ARCnet and netrom (AMPR NET/ROM).
multicast
Set the multicast flag on the interface. This should not normally be
needed because the drivers set the flag correctly themselves.
address
The IP address to be assigned to this interface.
txqueuelen length
Sets the length of the transmit queue of the device. It is useful to set
this to small values for slower devices with a high latency (modem links,
ISDN). This prevents fast bulk transfers from disturbing inter- active
traffic (like telnet) too much.
You may use the ifconfig command on any network interface. Some user
programs such as pppd and dip automatically configure the network devices
as they create them, so manual use of ifconfig is unnecessary.
Was_this_section_helpful?_Why_not_Donate_$2.50?
-------------------------------------------------------------------------------
5.5. Configuring your Name Resolver.
The `Name Resolver' is a part of the linux standard library. Its prime function
is to provide a service to convert human-friendly hostnames (like
`ftp.funet.fi' ) into machine friendly IP addresses (such as 128.214.248.6).
-------------------------------------------------------------------------------
5.5.1. What's in a name ?
You will probably be familiar with the appearance of Internet host names, but
you may not understand how they are constructed or de-constructed. Internet
domain names are hierarchical in nature. In other words, they have a tree-like
structure. A `domain' is a family, or group, of names. A `domain' may be broken
down into a `subdomain'. A `top level domain' is a domain that is not a
subdomain. The Top Level Domains are specified in RFC-920. Some examples of the
most common top level domains are:
COM
Commercial Organizations
EDU
Educational Organizations
GOV
Government Organizations
MIL
Military Organizations
ORG
Other Organizations
NET
Internet-Related Organizations
Country Designator
These are two- letter codes that represent a particular country.
For historical reasons, most domains belonging to one of the non-country based
top level domains were used by organizations within the United States (even
though the United States also has its own country code `.us'). This is not true
any more for .com and .org domains, which are commonly used by non-us
companies.
Each of these top level domains has subdomains. The top level domains based on
country name are often next broken down into subdomains based on the com, edu,
gov, mil and org domains. So for example you end up with: com.au and gov.au for
commercial and government organizations in Australia; note that this is not a
general rule, as actual policies depend on the naming authority for each
domain.
The next level of division usually represents the name of the organization.
Further subdomains vary in nature. Often the next level of subdomain is based
on the departmental structure of the organization. It can, however, be based on
any criterion considered reasonable and meaningful by the network
administrators of the organization.
The very left-most portion of the name is always the unique name assigned to
the host machine. It is called the `hostname'. The portion of the name to the
right of the hostname is called the `domainname' and the complete name is
called the `Fully Qualified Domain Name'.
To use Terrys host as an example, the fully qualified domain name is
`perf.no.itg.telstra.com.au'. This means that the host name is `perf' and the
domain name is `no.itg.telstra.com.au'. The domain name is based on a top level
domain (based on his country Australia). And since his email address belongs to
a commercial organization, `.com' is positioned as the next level domain. The
name of the company is (was) `Telstra' . Their internal naming structure is
based on organizational structure. In this case, the machine belongs to the
Information Technology Group (Network Operations section).
Usually, the names are much shorter. For example, my ISP is called
``systemy.it'' . My non-profit organization is called ``linux.it'', without any
com and org subdomain. My own host is just called ``morgana.systemy.it'' :
rubini@linux.it is a valid email address. Note that the owner of a domain has
the rights to register hostnames as well as subdomains. For example, the LUG I
belongs to uses the domain pluto.linux.it, because the owners of linux.it
agreed to open a subdomain for the LUG.
-------------------------------------------------------------------------------
5.5.2. What information you will need.
You will need to know what domain your hosts name will belong to. The name
resolver software provides this name translation service by making requests to
a `Domain Name Server'. You will need to know the IP address of a local name
server that you can use.
There are three files you need to edit. I'll cover each of these in turn.
-------------------------------------------------------------------------------
5.5.3. /etc/resolv.conf
The /etc/resolv.conf is the main configuration file for the name resolver code.
Its format is quite simple. It is a text file that has one keyword per line.
There are three keywords typically used by the file. These keywords are:
domain
This keyword specifies the local domain name.
search
This keyword specifies a list of alternate domain names to search for a
hostname
name server
This keyword, which may be used many times, specifies an IP address of a
domain name server to query when resolving names
An example /etc/resolv.conf might look something like:
_________________________________
|domain maths.wu.edu.au |
| search maths.wu.edu.au wu.edu.au|
| name server 192.168.10.1 |
| name_server_192.168.12.1________|
This example specifies that the default domain name to append to unqualified
names (ie hostnames supplied without a domain) is maths.wu.edu.au . If the host
is not found in that domain, it will also try the wu.edu.au domain directly.
Two name server entries are supplied. These entries may be called upon by the
name resolver code to resolve the name.
-------------------------------------------------------------------------------
5.5.4. /etc/host.conf
The /etc/host.conf file is where you configure some items that govern the
behavior of the name resolver code. The format of this file is described in
detail in the `resolv+' man page. In nearly all circumstances, the following
example will work for you:
________________
|order hosts,bind|
| multi_on_______|
This configuration tells the name resolver to check the /etc/hosts file before
attempting to query a name server. It also tells the resolver to return all
valid addresses for a host found in the /etc/hosts file (instead of just the
first address).
-------------------------------------------------------------------------------
5.5.5. /etc/hosts
The /etc/hosts file is where you put the name and IP address of local hosts. If
you place a host in this file, then you do not need to query the domain name
server to get its IP Address. The disadvantage of doing this is that if the IP
address for that host changes, you must keep this file up to date yourself . In
a well managed system, the only hostnames that usually appear in this file are
an entry for the loopback interface, and also the local hosts name.
__________________________________
|# /etc/hosts |
| 127.0.0.1 localhost loopback|
| 192.168.0.1____this.host.name____|
You may specify more than one host name per line (as demonstrated by the first
entry), which is a standard entry for the loopback interface.
-------------------------------------------------------------------------------
5.5.6. Running a name server
If you want to run a local name server, you can do it easily. Please refer to
the DNS-HOWTO and to any documents included in your version of BIND (Berkeley
Internet Name Domain).
-------------------------------------------------------------------------------
5.6. Configuring your loopback interface.
The `loopback' interface is a special type of interface that allows you to make
connections to yourself. There are various reasons why you might want to do
this. For example, you may wish to test some network software without
interfering with anybody else on your network. By convention, the IP address
`127.0.0.1' has been assigned specifically for loopback. No matter what machine
you go to, if you open a telnet connection to 127.0.0.1 you will always reach
the local host.
Configuring the loopback interface is simple, and it must be done (but note
that this task is usually performed by the standard initialization scripts).
___________________________________
|root# ifconfig lo 127.0.0.1 |
| root#_route_add_-host_127.0.0.1_lo|
We'll talk more about the route command in the next section. Was_this_section
helpful?_Why_not_Donate_$2.50?
-------------------------------------------------------------------------------
5.7. Routing.
Routing is a big topic. It is easily possible to write large volumes of text
about the subject. Most of you will have fairly simple routing requirements;
some of you will not. I will cover some basic fundamentals of routing only. If
you are interested in more detailed information, then I suggest you refer to
the references provided at the start of this document.
Let's start with a definition. What is IP routing? Here is one that I'm using:
"IP Routing is the process by which a host with multiple network connections
decides where to deliver the IP datagrams that it has received."
It might be useful to illustrate this with an example. Imagine a typical office
router. It might have a PPP link off the Internet, a number of Ethernet
segments feeding the workstations, and another PPP link off to another office.
When the router receives a datagram on any of its network connections, it uses
the routing mechanism to determine which interface it should send the datagram
to next. Simple hosts also need to route. All Internet hosts have two network
devices, one is the loopback interface described above, and the other is the
one it uses to talk to the rest of the network (perhaps an Ethernet, perhaps a
PPP, or an SLIP serial interface).
Ok, so how does routing work ? Each host keeps a special list of routing rules
called a "routing table". This table contains rows which typically contain at
least three fields: the first is a destination address, the second is the name
of the interface where the datagram is to be routed, and the third is
optionally the IP address of another machine that carries the datagram on its
next step through the network. You can see this table in linux by using the
following command:
_________________________
|user%_cat_/proc/net/route|
or by using either of the following commands:
____________________
|user% /sbin/route -n|
| user%_netstat_-r___|
The routing process is fairly simple. The incoming datagram is received, the
destination address (who it is for) is examined, and then it is compared with
each entry in the table. The entry that best matches that address is selected,
and the datagram is forwarded to the specified interface. If the gateway field
is filled, then the datagram is forwarded to that host via the specified
interface. The destination address is otherwise assumed to be on the network
supported by the interface.
To manipulate this table, a special command is used. This command takes command
line arguments and converts them into kernel system calls. These calls request
the kernel to add, delete, or modify entries in the routing table. The command
is called `route'.
Here is a simple example. Imagine you have an Ethernet network. You've been
told it is a class-C network with an address of 192.168.1.0. You've been
supplied with an IP address of 192.168.1.10 for your use, and you have been
told that 192.168.1.1 is a router connected to the Internet.
The first step is to configure the interface as described earlier. You would
use a command similar to the following:
_________________________________________________________
|root#_ifconfig_eth0_192.168.1.10_netmask_255.255.255.0_up|
You now need to add an entry into the routing table to tell the kernel that
datagrams for all hosts with addresses that match 192.168.1.* should be sent to
the ethernet device. You would use a command similar to:
___________________________________________________________
|root#_route_add_-net_192.1Ethernetetmask_255.255.255.0_eth0|
Note the use of the `-net' argument to tell the route program that this entry
is a network route. Your other choice here is a `-host' route, which is a route
that is specific to one IP address.
This route will enable you to establish IP connections with all of the hosts on
your ethernet segment. But what about all of the IP hosts that aren't on your
ethernet segment?
It would be a very difficult job to have to add routes to every possible
destination network. There is a special trick that is used to simplify this
task. The trick is called the `default' route. The default route matches every
possible destination (but poorly). If any other entry exists that matches the
required address, it will be used instead of the default route. The idea of the
default route is simply to enable you to say in effect: "and everything else
should go here". In this example you would use an entry like:
___________________________________________________________________________
|root# route add default gw 192.168.1.1 eth0 on|
|them_______________________________________________________________________|
The `gw' argument tells the route command that the next argument is the IP
address, or name, of a gateway or router machine. This machine is where all
datagrams matching the entry should be directed to for further routing. on them
So, your complete configuration would look like:
____________________________________________________________________________
|root# ifconfig eth0 192.168.1.10 netmask 255.255.255.0 up |
| root# route add -net 192.168.1.0 netmask 255.255.255.0 eth0 |
| root# route add default gw 192.168.1.1 eth0 on|
|them________________________________________________________________________|
is
If you take a close look at your network `rc' files, you will find that at
least one of them looks very similar to this configuration (a very common one).
Let's now look at a slightly more complicated routing configuration. Let's
imagine we are configuring the router we looked at earlier (the one supporting
the PPP link to the Internet, and the lan segments feeding the workstations in
the office). Lets imagine the router has three ethernet segments, and it also
has one PPP link. Our routing configuration would look something like the
fEthernet:
____________________________________________________________
|root# route add -net 192.168.1.0 netmask 255.255.255.0 eth0 |
| root# route add -net 192.168.2.0 netmask 255.255.255.0 eth1|
| root# route add -net 192.168.3.0 netmask 255.255.255.0 eth2|
| root#_route_add_default_ppp0_______________________________|
Each of the workstations would use the simpler form presented above. Only the
router needs to specify each of the network routes separately. The default
route for the workstations mechanism will capture all of them, letting the
router worry about splitting them up appropriately. You may be wondering why
the default route presented doesn't specify a `gw'. The reason for this is
simple: serial link protocols such as PPP and SLIP only have two hosts on their
network (one at each end). To specify the host at the other end of the link as
the gateway is both pointless and redundant. You do not need to specify a
gateway for these types of network connections as there is no other choice.
Other network types, such as ethernet, arcnet, or token ring, do actually
require the gateway to be specified (as these networks support Ethernetmbers of
hosts ).
-------------------------------------------------------------------------------
5.7.1. So what does the routed program do ?
The routing configuration described above is best suited for simple network
arrangements where there are only single possible paths to destinations. When
you have a more complex network arrangement, things get a little more
complicated. Fortunately for most of you this won't be an issue.
The big problem with `manual routing' or `static routing' is that if a machine
or link fails in your network, the only way to re-direct your datagrams (if
another way in fact exists) is by manually intervening and executing the
appropriate commands. Naturally this is clumsy, slow, impractical, and hazard
prone. Various techniques have been developed to automatically adjust routing
tables in the event of network failures (where there are alternate routes). All
of these techniques are loosely grouped by the term `dynamic routing
protocols'.
You may have heard of some of the more common dynamic routing protocols. The
most common are probably RIP (Routing Information Protocol) and OSPF (Open
Shortest Path First Protocol). The Routing Information Protocol is very common
on small networks (such as small-medium sized corporate networks or building
networks). OSPF is more modern. It is more capable at handling large network
configurations, and it is better suited to environments where there is a large
number of possible paths through the network. Common implementations of these
protocols are: `routed' - RIP and `gated' - RIP, OSPF and others. The `routed'
program is normally supplied with your Linux distribution, or it is included in
the `NetKit' package detailed above.
An example of where and how you might use a dynamic routing protocol might look
something like the following:
____________________________________________________________
| |
| 192.168.1.0 / 192.168.2.0 / |
| 255.255.255.0 255.255.255.0|
| - - |
| | | |
| | /-----\ /-----\ | |
| | | |ppp0 // ppp0| | | |
| eth0 |---| A |------//---------| B |---| eth0 |
| | | | // | | | |
| | \-----/ \-----/ | |
| | \ ppp1 ppp1 / | |
| - \ / - |
| \ / |
| \ / |
| \ / |
| \ / |
| \ / |
| \ / |
| \ / |
| \ / |
| ppp0\ /ppp1 |
| /-----\ |
| | | |
| | C | |
| | | |
| \-----/ |
| |eth0 |
| | |
| |---------| |
| 192.168.3.0 / |
| 255.255.255.0 |
|____________________________________________________________|
We have three routers A, B and C. Each router supports one ethernet segment
with a Class C IP network (netmask 255.255.255.0). Each one also has a PPP link
to each of tEthernet routers. The network ultimately forms a triangle.
It should be clear that the routing table at router A could look like the
following:
______________________________________________________________
|root# route add -net 192.168.1.0 netmask 255.255.255.0 eandth0|
| root# route add -net 192.168.2.0 netmask 255.255.255.0 ppp0 |
| root#_route_add_-net_192.168.3.0_netmask_255.255.255.0_ppp1__|
This would work just fine until the link between router A and B fails. Hosts on
the ethernet segment of A (see above diagram) could not reach hosts on the
ethernet segment on B: their datagramEthernete directed to router As ppp0 link
(which in this example is broEthernetey could still continue to talk to hosts
on the ethernet segment of C. And hosts on CCsethernet segment could still talk
to hosts on BBsethernet segment. TheEthernetnications can still occur because
the link between B and C is still intact.
If A can talk to C, and C can still talk to B, why shouldn't A route its
datagrams for B via C (and let C send them to B) ? This is exactly the sort of
problem that dynamic routing protocols like RIP were designed to solve. If each
of the routers A, B and C were running a routing daemon, then their routing
tables would be automatically adjusted to reflect the new state of the network
(should any one of the links in the network fail). To configure such a network
is simple: at each router you need only do two things. In this case for Router
A:
___________________________________________________________
|root# route add -net 192.168.1.0 netmask 255.255.255.0 eth0|
| root#_/usr/sbin/routed____________________________________|
The `routed' routing daemon automatically finds all active network ports (when
it sends and listens for messages on each of the network devices) to allow it
to both determine and update the routing table on the host.
This has been a very brief explanation of dynamic routing. If you would like
more information, please refer to the suggested references listed at the top of
this document.
The important points relating to dynamic routing are:
1. You only need to run a dynamic routing protocol daemon when your Linux
machine has the possibility of selecting multiple route alternatives to a
destination. An example of this would be if you plan to use IP
Masquerading.
2. The dynamic routing daemon will automatically modify your routing table to
adjust to changes in your network.
3. RIP is suitable for small to medium sized networks.
-------------------------------------------------------------------------------
5.8. Configuring your network servers and services.
Network servers and services are programs that allow a remote user to make use
of your Linux machine. Server programs listen on network ports. Network ports
are a means of addressing a particular service on any particular host. They are
how a server knows the difference between an incoming telnet connection and an
incoming ftp connection. The remote user establishes a network connection to
your machine. The server program (the network daemon program) listening on that
port accepts the connection and then executes. There are two ways that network
daemons may operate. Both are commonly employed in practice. The two ways are:
sstand-alone
The network daemon program listens on the designated network port. When
an incoming connection is made, the daemon manages the network connection
itself to provide the service.
slave to the inetd server
The inetd server is a special network daemon program that specializes in
managing incoming network connections. It has a configuration file which
tells it what program needs to be run upon receiving an incoming
connection. Any service port may be configured for either of the tcp or
udp protocols. The ports are described in another file that we will soon
review..
There are two important files that need to be configured. They are the /etc/
services file (which assigns names to port numbers), and the /etc/inetd.conf
file (the configuration file for the inetd network daemon).
-------------------------------------------------------------------------------
5.8.1. /etc/services
The /etc/services file is a simple database that associates a human friendly
name to a machine friendly service port. Its format is quite simple. The file
is a text file where each line represents and entry in the database. Each entry
is comprised of three fields separated by any number of whitespace (tab or
space) characters. The fields are:
name port/protocol aliases # comment
name
A single word name that represents the service being described.
port/protocol
This field is split into two subfields.
port
A number that specifies the port number where the named service will be
available. Most of the common services have assigned service numbers.
These are described in RFC-1340.
protocol
This subfield may be set to either tcp or udp.
It is important to note that an entry of 18/tcp is very different from an
entry of 18/udp There is no technical reason why the same service needs
to exist on both. Normally common sense prevails. It is only if a
particular service is available via both tcp and udp that you will see an
entry for both.
aliases
Other names that may be used to refer to this service entry.
Any text appearing in a line after a `#' character is ignored, and it is
treated as a comment.
-------------------------------------------------------------------------------
5.8.1.1. An example /etc/services file.
All modern linux distributions provide a good /etc/services file. Just in case
you happen to be building a machine from the ground up, here is a copy of the /
etc/services file supplied with an old Debian distribution:
_____________________________________________________________________________
| |
| # /etc/services: |
| # $Id$ |
| # |
| # Network services, Internet style |
| # |
| # Note that it is presently the policy of IANA to assign a single well- |
| known |
| # port number for both TCP and UDP; hence, most entries here have two |
| entries |
| # even if the protocol doesn't support UDP operations. |
| # Updated from RFC 1340, ``Assigned Numbers'' (July 1992). Not all ports |
| # are included (only the more common ones): |
| tcpmux 1/tcp # TCP port service multiplexer |
| echo 7/tcp |
| echo 7/udp |
| discard 9/tcp sink null |
| discard 9/udp sink null |
| systat 11/tcp users |
| daytime 13/tcp |
| daytime 13/udp |
| netstat 15/tcp |
| qotd 17/tcp quote |
| msp 18/tcp # message send protocol |
| msp 18/udp # message send protocol |
| chargen 19/tcp ttytst source |
| chargen 19/udp ttytst source |
| ftp-data 20/tcp |
| ftp 21/tcp |
| ssh 22/tcp # SSH Remote Login Protocol |
| ssh 22/udp # SSH Remote Login Protocol |
| telnet 23/tcp |
| # 24 - private |
| smtp 25/tcp mail |
| # 26 - unassigned |
| time 37/tcp timserver |
| time 37/udp timserver |
| rlp 39/udp resource # resource location |
| nameserver 42/tcp name # IEN 116 |
| whois 43/tcp nicname |
| re-mail-ck 50/tcp # Remote Mail Checking Protoconame server |
| re-mail-ck 50/udp # Remote Mail Checking Protocol |
| domain 53/tcp nameserver # name-domain server |
| domain 53/udp nameserver |
| mtp 57/tcp # deprecated |
| bootps 67/tcname serverTP server |
| bootps 67/udp |
| bootpc 68/tcname serverTP client |
| bootpc 68/udp |
| tftp 69/udp |
| gopher 70/tcp # Internet Gopher |
| gopher 70/udp |
| rje 77/tcp netrjs |
| finger 79/tcp |
| www 80/tcp http # WorldWideWeb HTTP |
| www 80/udp # HyperText Transfer Protocol |
| link 87/tcp ttylink |
| kerberos 88/tcp kerberos5 krb5 # Kerberos v5 |
| kerberos 88/udp kerberos5 krb5 # Kerberos v5 |
| supdup 95/tcp |
| # 100 - reserved |
| hostnames 101/tcp hostname # usually from sri-nic |
| iso-tsap 102/tcp tsap # part of ISODE. |
| csnet-ns 105/tcp cso-ns # also used by CSO name server |
| csnet-ns 105/udp cso-ns |
| rtelnet 107/tcp # Remote Telnet |
| rtelnet 107/udp |
| pop-2 109/tcp postoffice # POP version 2 |
| pop-2 109/udp |
| pop-3 110/tcp # POP version 3 |
| pop-3 110/udp |
| sunrpc 111/tcp portmapper # RPC 4.0 portmapper TCP |
| sunrpc 111/udp portmapper # RPC 4.0 portmapper UDP |
| auth 113/tcp authentication tap ident |
| sftp 115/tcp |
| uucp-path 117/tcp |
| nntp 119/tcp readnews untp # USENET News Transfer Protocol |
| ntp 123/tcp |
| ntp 123/udp # Network Time Protocol |
| netbios-ns 137/tcp # NETBIOS Name Service |
| netbios-ns 137/udp |
| netbios-dgm 138/tcp # NETBIOS Datagram Service |
| netbios-dgm 138/udp |
| netbios-ssn 139/tcp # NETBIOS session service |
| netbios-ssn 139/udp |
| imap2 143/tcp # Interim Mail Access Proto v2 |
| imap2 143/udp |
| snmp 161/udp # Simple Net Mgmt Proto |
| snmp-trap 162/udp snmptrap # Traps for SNMP |
| cmip-man 163/tcp # ISO mgmt over IP (CMOT) |
| cmip-man 163/udp |
| cmip-agent 164/tcp |
| cmip-agent 164/udp |
| xdmcp 177/tcp # X Display Mgr. Control Proto |
| xdmcp 177/udp |
| nextstep 178/tcp NeXTStep NextStep # NeXTStep window |
| nextstep 178/udp NeXTStep NextStep # server |
| bgp 179/tcp # Border Gateway Proto. |
| bgp 179/udp |
| prospero 191/tcp # Cliff Neuman's Prospero |
| prospero 191/udp |
| irc 194/tcp # Internet Relay Chat |
| irc 194/udp |
| smux 199/tcp # SNMP Unix Multiplexer |
| smux 199/udp |
| at-rtmp 201/tcp # AppleTalk routing |
| at-rtmp 201/udp |
| at-nbp 202/tcp # AppleTalk name binding |
| at-nbp 202/udp |
| at-echo 204/tcp # AppleTalk echo |
| at-echo 204/udp |
| at-zis 206/tcp # AppleTalk zone information |
| at-zis 206/udp |
| z3950 210/tcp wais # NISO Z39.50 database |
| z3950 210/udp wais |
| ipx 213/tcp # IPX |
| ipx 213/udp |
| imap3 220/tcp # Interactive Mail Access |
| imap3 220/udp # Protocol v3 |
| ulistserv 372/tcp # UNIX Listserv |
| ulistserv 372/udp |
| # |
| # UNIX specific services |
| # |
| exec 512/tcp |
| biff 512/udp comsat |
| login 513/tcp |
| who 513/udp whod |
| shell 514/tcp cmd # no passwords used |
| syslog 514/udp |
| printer 515/tcp spooler # line printer spooler |
| talk 517/udp |
| ntalk 518/udp |
| route 520/udp router routed # RIP |
| timed 525/udp timeserver |
| tempo 526/tcp newdate |
| courier 530/tcp rpc |
| conference 531/tcp chat |
| netnews 532/tcp readnews |
| netwall 533/udp # -for emergency broadcasts |
| uucp 540/tcp uucpd # uucp daemon |
| remotefs 556/tcp rfs_server rfs # Brunhoff remote filesystem |
| klogin 543/tcp # Kerberized `rlogin' (v5) |
| kshell 544/tcp krcmd # Kerberized `rsh' (v5) |
| kerberos-adm 749/tcp # Kerberos `kadmin' (v5) |
| # |
| webster 765/tcp # Network dictionary |
| webster 765/udp |
| # |
| # From ``Assigned Numbers'': |
| # |
| #> The Registered Ports are not controlled by the IANA and on most systems |
| #> can be used by ordinary user processes or programs executed by ordinary |
| #> users. |
| # |
| #> Ports are used in the TCP [45,106] to name the ends of logical |
| #> connections which carry long term conversations. For the purpose of |
| #> providing services to unknown callers, a service contact port is |
| #> defined. This list specifies the port used by the server process as its|
| #> contact port. While the IANA can not control uses of these ports it |
| #> does register or list uses of these ports as a convenience to the |
| #> community. |
| # |
| ingreslock 1524/tcp |
| ingreslock 1524/udp |
| prospero-np 1525/tcp # Prospero non-privileged |
| prospero-np 1525/udp |
| rfe 5002/tcp # Radio Free Ethernet |
| rfe 5002/udp # Actually uses UDP only |
| bbs 7000/tcp # BBS service |
| # |
| # |
| # Kerberos (Project Athena/MIT) services |
| # Note that these are for Kerberos v4 and are unofficial. Sites running |
| # v4 should uncomment these and comment out the v5 entries above. |
| # |
| kerberos4 750/udp kdc # Kerberos (server) udp |
| kerberos4 750/tcp kdc # Kerberos (server) tcp |
| kerberos_master 751/udp # Kerberos authentication |
| kerberos_master 751/tcp # Kerberos authentication |
| passwd_server 752/udp # Kerberos passwd server |
| krb_prop 754/tcp # Kerberos slave propagation |
| krbupdate 760/tcp kreg # Kerberos registration |
| kpasswd 761/tcp kpwd # Kerberos "passwd" |
| kpop 1109/tcp # Pop with Kerberos |
| knetd 2053/tcp # Kerberos de-multiplexor |
| zephyr-srv 2102/udp # Zephyr server |
| zephyr-clt 2103/udp # Zephyr serv-hm connection |
| zephyr-hm 2104/udp # Zephyr hostmanager |
| eklogin 2105/tcp # Kerberos encrypted rlogin |
| # |
| # Unofficial but necessary (for NetBSD) services |
| # |
| supfilesrv 871/tcp # SUP server |
| supfiledbg 1127/tcp # SUP debugging |
| # |
| # Datagram Delivery Protocol services |
| # |
| rtmp 1/ddp # Routing Table Maintenance Protocol |
| nbp 2/ddp # Name Binding Protocol |
| echo 4/ddp # AppleTalk Echo Protocol |
| zip 6/ddp # Zone Information Protocol |
| # |
| # Debian GNU/Linux services |
| rmtcfg 1236/tcp # Gracilis Packeten remote config server |
| xtel 1313/tcp # french minitel |
| cfinger 2003/tcp # GNU Finger |
| postgres 4321/tcp # POSTGRES |
| mandelspawn 9359/udp mandelbrot # network mandelbrot |
| # Local services |
|_____________________________________________________________________________|
In the real world, the actual file is always growing as new services are being
created. If you fear your own copy is incomplete, I'd suggest to copy a new /
etc/services from a recent distribution.
-------------------------------------------------------------------------------
5.8.2. /etc/inetd.conf
The /etc/inetd.conf file is the configuration file for the inetd server daemon.
Its function is to tell inetd what to do when it receives a connection request
for a particular service. For each service that you wish to accept connections,
you must tell inetd what network server daemon to run (and how to run it).
Its format is also fairly simple. It is a text file with each line describing a
service that you wish to provide. Any text in a line following a `#' is both
ignored, and it is considered a comment. Each line contains seven fields
separated by any number of whitespace (tab or space) characters. The general
format is as follows:
______________________________________________________________________
| |
| service socket_type proto flags user server_path server_args|
|______________________________________________________________________|
service
Is the service relevant to this configuration as taken from the /etc/
services file.
socket_type
This field describes the type of socket that this entry will consider
relevant. Allowable values are: stream, dgram, raw, rdm, or seqpacket.
This is a little technical in nature. As a rule of thumb nearly all tcp
based services use stream, and nearly all udp based services use dgram.
It is only very special types of server daemons that would use any of the
other values.
proto
The protocol to be considered valid for this entry. This should match the
appropriate entry in the /etc/services file. It will typically be either
tcp or udp. Sun RPC (Remote Procedure Call) based servers will use
eitherrpc/tcp or rpc/udp.
flags
There are really only two possible settings for this field. This field
setting tells inetd whether the network server program frees the socket
after it has been started (whether inetd can start another one on the
next connection request), or, whether inetd should wait and assume that
any server daemon already running will handle the new connection request.
This is a little tricky to work out, but as a rule of thumb all tcp
servers should have this entry set to nowait. Most udp servers should
have this entry set to wait. Be warned there are some notable exceptions.
You should let the example guide you if you are not sure.
user
This field describes which user account from /etc/passwd will be set as
the owner of the network daemon when it is started. This is often useful
if you want to safeguard against security risks. You can set the user of
an entry to the nobody user. If the network server security is breached,
the possible damage is minimized by using nobody. Typically this field is
set to root, because many servers require root privileges in order to
function correctly.
server_path
This field is pathname to the athoughctual server program to execute for
this entry.
server_args
This field comprises the rest of the line and it is optional. This field
is where you place any command line arguments that you wish to pass to
the server daemon program when it is launched.
-------------------------------------------------------------------------------
5.8.2.1. An example /etc/inetd.conf
As for the /etc/services file all modern distributions will include a good /
etc/inetd.conf file for you to work with. Here is the /etc/inetd.conf file from
the Debian distribution.
____________________________________________________________________________
| |
| # /etc/inetd.conf: see inetd(8) for further informations. |
| # |
| # Internet server configuration database |
| # |
| # |
| # Modified for Debian by Peter Tobias <tobias@et-inf.fho-emden.de> |
| # |
| # <service_name> <sock_type> <proto> <flags> <user> <server_path> <args> |
| # |
| # Internal services |
| # |
| #echo stream tcp nowait root internal |
| #echo dgram udp wait root internal |
| discard stream tcp nowait root internal |
| discard dgram udp wait root internal |
| daytime stream tcp nowait root internal |
| daytime dgram udp wait root internal |
| #chargen stream tcp nowait root internal |
| #chargen dgram udp wait root internal |
| time stream tcp nowait root internal |
| time dgram udp wait root internal |
| # |
| # These are standard services. |
| # |
| telnet stream tcp nowait root /usr/sbin/tcpd /usr/sbin/in.telnetd |
| ftp stream tcp nowait root /usr/sbin/tcpd /usr/sbin/in.ftpd |
| #fsp dgram udp wait root /usr/sbin/tcpd /usr/sbin/in.fspd |
| # |
| # Shell, login, exec and talk are BSD protocols. |
| # |
| shell stream tcp nowait root /usr/sbin/tcpd /usr/sbin/in.rshd |
| login stream tcp nowait root /usr/sbin/tcpd /usr/sbin/in.rlogind |
| #exec stream tcp nowait root /usr/sbin/tcpd /usr/sbin/in.rexecd |
| talk dgram udp wait root /usr/sbin/tcpd /usr/sbin/in.talkd |
| ntalk dgram udp wait root /usr/sbin/tcpd /usr/sbin/in.ntalkd |
| # |
| # Mail, news and uucp services. |
| # |
| smtp stream tcp nowait root /usr/sbin/tcpd /usr/sbin/in.smtpd |
| #nntp stream tcp nowait news /usr/sbin/tcpd /usr/sbin/in.nntpd |
| #uucp stream tcp nowait uucp /usr/sbin/tcpd /usr/lib/uucp/uucico |
| #comsat dgram udp wait root /usr/sbin/tcpd /usr/sbin/in.comsat |
| # |
| # Pop et al |
| # |
| #pop-2 stream tcp nowait root /usr/sbin/tcpd /usr/sbin/in.pop2d |
| #pop-3 stream tcp nowait root /usr/sbin/tcpd /usr/sbin/in.pop3d |
| # |
| # `cfinger' is for the GNU finger server available for Debian. (NOTE: The|
| # current implementation of the `finger' daemon allows it to be run as |
| `root'.) |
| # |
| #cfinger stream tcp nowait root /usr/sbin/tcpd /usr/sbin/in.cfingerd |
| #finger stream tcp nowait root /usr/sbin/tcpd /usr/sbin/in.fingerd |
| #netstat stream tcp nowait nobody /usr/sbin/tcpd /bin/netstat |
| #systat stream tcp nowait nobody /usr/sbin/tcpd /bin/ps -auwwx |
| # |
| # Tftp service is provided primarily for booting. Most sites |
| # run this only on machines acting as "boot servers." |
| # |
| #tftp dgram udp wait nobody /usr/sbin/tcpd /usr/sbin/in.tftpd |
| #tftp dgram udp wait nobody /usr/sbin/tcpd /usr/sbin/in.tftpd /boot |
| #bootps dgram udp wait root /usr/sbin/bootpd bootpd -i -t 120 |
| # |
| # Kerberos authenticated services (these probably need to be corrected) |
| # |
| #klogin stream tcp nowait root /usr/sbin/tcpd /usr/sbin/in.rlogind -k |
| #eklogin stream tcp nowait root /usr/sbin/tcpd /usr/sbin/in.rlogind -k -x |
| #kshell stream tcp nowait root /usr/sbin/tcpd /usr/sbin/in.rshd -k |
| # |
| # Services run ONLY on the Kerberos server (these probably need to be |
| corrected) |
| # |
| #krbupdate stream tcp nowait root /usr/sbin/tcpd /usr/sbin/registerd |
| #kpasswd stream tcp nowait root /usr/sbin/tcpd /usr/sbin/kpasswdd |
| # |
| # RPC based services |
| # |
| #mountd/1 dgram rpc/udp wait root /usr/sbin/tcpd /usr/sbin/rpc.mountd |
| #rstatd/1-3 dgram rpc/udp wait root /usr/sbin/tcpd /usr/sbin/rpc.rstatd |
| #rusersd/2-3 dgram rpc/udp wait root /usr/sbin/tcpd /usr/sbin/rpc.rusersd |
| #walld/1 dgram rpc/udp wait root /usr/sbin/tcpd /usr/sbin/rpc.rwalld |
| # |
| # End of inetd.conf. |
| ident stream tcp nowait nobody /usr/sbin/identd identd -i |
|____________________________________________________________________________|
-------------------------------------------------------------------------------
5.9. Other miscellaneous network related configuration files.
There are a number of miscellaneous files relating to network configuration
under linux that might be of interest. You may never have to modify these
files, but it is worth describing them so you know what they contain and why
they are used.
-------------------------------------------------------------------------------
5.9.1. /etc/protocols
The /etc/protocols file is a database that maps protocol id numbers against
protocol names. This is used by programmers to allow them to specify protocols
by name in their programs. The file is also used by some programs such as
tcpdump to allow them to display names instead of numbers in their output. The
general syntax of the file is:
_________________________________
| |
| protocolname number aliases|
|_________________________________|
The /etc/protocols file supplied with the Debian distribution is as follows:
_______________________________________________________________________
| |
| # /etc/protocols: |
| # $Id$ |
| # |
| # Internet (IP) protocols |
| # |
| # from: @(#)protocols 5.1 (Berkeley) 4/17/89 |
| # |
| # Updated for NetBSD based on RFC 1340, Assigned Numbers (July 1992).|
| ip 0 IP # Internet protocol, pseudo protocol number |
| icmp 1 ICMP # Internet control message protocol |
| igmp 2 IGMP # Internet Group Management |
| ggp 3 GGP # gateway-gateway protocol |
| ipencap 4 IP-ENCAP # IP encapsulated in IP (officially ``IP'') |
| st 5 ST # ST datagram mode |
| tcp 6 TCP # transmission control protocol |
| egp 8 EGP # exterior gateway protocol |
| pup 12 PUP # PARC universal packet protocol |
| udp 17 UDP # user datagram protocol |
| hmp 20 HMP # host monitoring protocol |
| xns-idp 22 XNS-IDP # Xerox NS IDP |
| rdp 27 RDP # "reliable datagram" protocol |
| iso-tp4 29 ISO-TP4 # ISO Transport Protocol class 4 |
| xtp 36 XTP # Xpress Tranfer Protocol |
| ddp 37 DDP # Datagram Delivery Protocol |
| idpr-cmtp 39 IDPR-CMTP # IDPR Control MessTransfernsport |
| rspf 73 RSPF # Radio Shortest Path First. |
| vmtp 81 VMTP # Versatile Message Transport |
| ospf 89 OSPFIGP # Open Shortest Path First IGP |
| ipip 94 IPIP # Yet Another IP encapsulation |
| encap 98 ENCAP # Yet Another IP encapsulation |
|_______________________________________________________________________|
-------------------------------------------------------------------------------
5.9.2. /etc/networks
The /etc/networks file has a similar function to that of the /etc/hosts
file.This file provides a simple database of network names against network
addresses. Its format differs in that there may be only two fields per line,
and that the fields are coded as:
______________________________
| |
| networkname networkaddress|
|______________________________|
An example might look like:
_______________________
|loopnet 127.0.0.0 |
| localnet 192.168.0.0|
| amprnet____44.0.0.0___|
You will get a display of the network name (NOT its address) while using a
command like route in the following instance: the destination is a network, and
that network has an entry in the /etc/networks file.
-------------------------------------------------------------------------------
5.10. Network Security and access control.
Let me start this section by warning you that securing your machine and network
against malicious attack is a complex art. I do not consider myself an expert
in this field. The following mechanisms I describe will help. If you are
serious about security, then I recommend you do some research of your own into
the subject. There are many good references on the Internet relating to the
security, including the Security-HOWTO
An important rule of thumb is: `Don't run servers you don't intend to use'.
Many distributions come configured with all sorts of services that are
configured and automatically started. To ensure even a minimum level of safety,
you should go through your /etc/inetd.conf file. Comment out (place a `#' at
the start of the line) any entries for services you don't intend to use. Good
candidates are services such as: shell, login, exec, uucp, ftp and
informational services such as finger, netstat and systat.
There are all sorts of security and access control mechanisms. I'll now
describe the most elementary:
-------------------------------------------------------------------------------
5.10.1. /etc/ftpusers
The /etc/ftpusers file is a simple mechanism that allows you to deny certain
users from logging into your machine via ftp. When an incoming ftp connection
is received, the /etc/ftpusers file is read by the ftp daemon program (ftpd).
The file is a simple list of those users who are not allowed login. It might
look something like:
____________________________________________________
|# /etc/ftpusers - users not allowed to login via ftp|
| root |
| uucp |
| bin |
| mail_______________________________________________|
-------------------------------------------------------------------------------
5.10.2. /etc/securetty
The /etc/securetty file allows you to specify which tty devices root are
allowed for login. The /etc/securetty file is read by the login program
(usually /bin/login). Its format is a list of the tty devices names allowed: on
all others root login is disallowed:
__________________________________________________________
|# /etc/securetty - tty's on which root is allowed to login|
| tty1 |
| tty2 |
| tty3 |
| tty4_____________________________________________________|
-------------------------------------------------------------------------------
5.10.3. The tcpd hosts access control mechanism.
The tcpd program listed in the samone /etc/inetd.conf provides logging and
access control mechanisms to services. It is configured to protect.
When it is invoked by the inetd program, it reads two files containing access
rules. It will then either alallow oreny access to the server it is protecting.
It will search the rules files until the first match is found. If no match is
found, then it assumes that access should be allowed to anyone. The files it
searches in sequence are: /etc/hosts.allow, /etc/hosts.deny. I'll describe each
of these in turn. For a complete description of this facility, you should refer
to the appropriate man pages (hosts_access(5) is a good starting point).
-------------------------------------------------------------------------------
5.10.3.1. /etc/hosts.allow
The /etc/hosts.allow file is a configuration file of the /usr/sbin/tcpd
program. The hosts.allow file contains rules describing which hosts are allowed
access to a service on your machine.
The file format is quite simple:
__________________________________________
|# /etc/hosts.allow |
| # |
| #_<service_list>:_<host_list>_[:_command]|
service list
This is a comma delimited list of server names where this rule applies.
Example server names are: ftpd, telnetd and fingerd.
host list
This is a comma delimited list of host names. You may also use IP
addresses here. You may additionally specify either hostnames or
addresses using wildcard characters to match groups of hosts. Examples
include: gw.vk2ktj.ampr.org to match a specific host, .uts.edu.au to
match any hostname ending in that string, 44. to match any IP address
commencing with those digits. There are some special tokens to simplify
configuration. Some of these are: ALL matches every host, LOCAL matches
any host whose name does not contain a `.' ie is in the same domain as
your machine and PARANOID matches any host whose name does not match its
address (name spoofing). There is one last token that is also useful. The
EXCEPT token allows you to provide a list with exceptions. This will be
covered in an example later.
command
This is an optional parameter. This parameter is the full pathname of a
command that would be executed everytime this rule is matched. It could,
for example, run a command that would attempt to identify who is logged
onto the connecting host. It could also generate a mail message or some
other warning to a system administrator that someone is attempting to
connect. There are a number of expansions that may be included. Some
common examples are: %h expands to the name of the connecting host or
address if it doesn't have a name, %d the daemon name being called.
An example:
____________________________________________________________________________
| |
| # /etc/hosts.allow |
| # |
| # Allow mail to anyone |
| in.smtpd: ALL |
| # All telnet and ftp to only hosts within my domain and my host at home.|
| telnetd, ftpd: LOCAL, myhost.athome.org.au |
| # Allow finger to anyone but keep a record of who they are. |
| fingerd: ALL: (finger @%h | mail -s "finger from %h" root) |
|____________________________________________________________________________|
-------------------------------------------------------------------------------
5.10.3.2. /etc/hosts.deny
The /etc/hosts.deny file is a configuration file of the /usr/sbin/tcpd program.
The hosts.deny file contains rules describing which hosts are disallowed access
to a service on your machine.
A simple sample would look something like this:
_______________________________________________
| |
| # /etc/hosts.deny |
| # |
| # Disallow all hosts with suspect hostnames|
| ALL: PARANOID |
| # |
| # Disallow all hosts. |
| ALL: ALL |
|_______________________________________________|
The PARANOID entry is redundant because the other entry traps everything in any
case. Either of these entries would make a reasonable default (depending on
your particular requirement).
Having an ALL: ALL default in the /etc/hosts.deny and then specifically
enabling on those services and hosts that you want in the /etc/hosts.allow file
is the safest configuration.
-------------------------------------------------------------------------------
5.10.4. /etc/hosts.equiv
The hosts.equiv file is used to grant certain hosts and users access rights to
accounts on your machine without having to supply a password. This is useful in
a secure environment where you control all machines, but is otherwise a
security hazard . Your machine is only as secure as the least secure of the
trusted hosts. To maximize security, don't use this mechanism. Encourage your
users not to use the .rhosts file as well.
-------------------------------------------------------------------------------
5.10.5. Configure your ftp daemon properly.
Many sites will be interested in running an anonymous ftp server to allow other
people to upload and download files without requiring a specific userid. If you
decide to offer this facility, make sure you configure the ftp daemon properly
for anonymous access. Most man pages for ftpd(8) describe in some length the
proper procedures. You should always ensure that you follow these instructions.
An important tip is to not use a copy of your /etc/passwd file in the anonymous
account /etc directory. Make sure you strip out all account details (except
those that you must have), otherwise you will be vulnerable to brute force
password cracking techniques.
-------------------------------------------------------------------------------
5.10.6. Network Firewalling.
Not allowing datagrams to even reach your machine (or servers) is an excellent
means of security. This is covered in depth in the Firewall-HOWTO, and (more
concisely) in a later section of this document.
-------------------------------------------------------------------------------
5.10.7. Other suggestions.
Here are some other (potentially religious) suggestions for you to consider:
sendmail
Despite its popularity, the sendmail daemon appears with frightening
regularity on security warning announcements. My recommendation is not to
run it.
NFS and other Sun RPC services
Be wary of these services. There are all sorts of possible exploits for
them. It is difficult finding an option to services like NFS. If you
configure them, make sure you are careful to whom you allow mount rights.
-------------------------------------------------------------------------------
Chapter 6. Ethernet Information
This section covers information specific to Ethernet, and it also covers the
configuring of Ethernet Cards.
-------------------------------------------------------------------------------
6.1. Supported Ethernet Cards
6.1.1. 3Com
* 3Com 3c501 - `Avoid like the plague!'' (3c501 driver)
* 3Com 3c503 (3c503 driver), 3c505 (3c505 driver), 3c507 (3c507 driver), 3c509/
3c509B (ISA) / 3c579 (EISA)
* 3Com Etherlink III Vortex Ethercards (3c590, 3c592, 3c595, 3c597) (PCI), 3Com
Etherlink XL Boomerang (3c900, 3c905) (PCI) and Cyclone (3c905B, 3c980)
Ethercards (3c59x driver) and 3Com Fast EtherLink Ethercard (3c515) (ISA)
(3c515 driver)
* 3Com 3ccfe575 Cyclone Cardbus (3c59x driver)
* 3Com 3c575 series Cardbus (3c59x driver) (ALL PCMCIA ??)
-------------------------------------------------------------------------------
6.1.2. AMD, ATT, Allied Telesis, Ansel, Apricot
* AMD LANCE (79C960) / PCnet-ISA/PCI (AT1500, HP J2405A, NE1500/NE2100)
* ATT GIS WaveLAN
* Allied Telesis AT1700
* Allied Telesis LA100PCI-T
* Allied Telesyn AT2400T/BT ("ne" module)
* Ansel Communications AC3200 (EISA)
* Apricot Xen-II / 82596
-------------------------------------------------------------------------------
6.1.3. Cabletron, Cogent, Crystal Lan
* Cabletron E21xx
* Cogent EM110
* Crystal Lan CS8920, Cs8900
-------------------------------------------------------------------------------
6.1.4. Danpex, DEC, Digi, DLink
* Danpex EN-9400
* DEC DE425 (EISA) / DE434/DE435 (PCI) / DE450/DE500 (DE4x5 driver)
* DEC DE450/DE500-XA (dc21x4x) (Tulip driver)
* DEC DEPCA and EtherWORKS
* DEC EtherWORKS 3 (DE203, DE204, DE205)
* DECchip DC21x4x "Tulip"
* DEC QSilver's (Tulip driver)
* Digi International RightSwitch
* DLink DE-220P, DE-528CT, DE-530+, DFE-500TX, DFE-530TX
-------------------------------------------------------------------------------
6.1.5. Fujitsu, HP, ICL, Intel
* Fujitsu FMV-181/182/183/184
* HP PCLAN (27245 and 27xxx series)
* HP PCLAN PLUS (27247B and 27252A)
* HP 10/100VG PCLAN (J2577, J2573, 27248B, J2585) (ISA/EISA/PCI)
* ICL EtherTeam 16i / 32 (EISA)
* Intel EtherExpress
* Intel EtherExpress Pro
-------------------------------------------------------------------------------
6.1.6. KTI, Macromate, NCR NE2000/1000, Netgear, New Media
* KTI ET16/P-D2, ET16/P-DC ISA (work jumperless andjumper lessware-
configuration options)
* Macromate MN-220P (PnP or NE2000 mode)
* NCR WaveLAN
* NE2000/NE1000 (be careful with clones)
* Netgear FA-310TX (Tulip chip)
* New Media Ethernet
-------------------------------------------------------------------------------
6.1.7. PureData, SEEQ, SMC
* PureData PDUC8028, PDI8023
* SEEQ 8005
* SMC Ultra / EtherEZ (ISA)
* SMC 9000 series
* SMC PCI EtherPower 10/100 (DEC Tulip driver)
* SMC EtherPower II (epic100.c driver)
-------------------------------------------------------------------------------
6.1.8. Sun Lance, Sun Intel, Schneider, WD, Zenith, IBM, Enyx
* Sun LANCE adapters (kernel 2.2 and newer)
* Sun Intel adapters (kernel 2.2 and newer)
* Schneider and Koch G16
* Western Digital WD80x3
* Zenith Z-Note / IBM ThinkPad 300 built-in adapter
* Znyx 312 etherarray (Tulip driver)
-------------------------------------------------------------------------------
6.2. General Ethernet Information
Ethernet devices names are `eth0', `eth1', `eth2' etc. The first card detected
by the kernel is assigned `eth0', and the rest are assigned sequentially in the
order in which they are detected.
Once you have your kernel properly built to support your ethernet card,
configuration of the card is easy.
Typically you would use something like (which most distributions already do for
you, if you configured them to support your ethernet):
____________________________________________________________
|root# ifconfig eth0 192.168.0.1 netmask 255.255.255.0 up |
| root#_route_add_-net_192.168.0.0_netmask_255.255.255.0_eth0|
Most of the ethernet drivers were developed by Donald_Becker Was_this_section
helpful?_Why_not_Donate_$2.50?
-------------------------------------------------------------------------------
6.3. Using 2 or more Ethernet Cards in the same machine
6.3.1. If your driver is a module (Normal with newer distros)
The module will typically can detect all of the installed cards.
Information from the detection is stored in the file:
/etc/conf.modules.
Consider that a user has 3 NE2000 cards, one at 0x300 one at 0x240, and one at
0x220. You would add the following lines to the /etc/conf.modules file:
__________________________________
| |
| alias eth0 ne |
| alias eth1 ne |
| alias eth2 ne |
| options ne io=0x220,0x240,0x300|
|__________________________________|
What this does is tell the program modprobe to look for 3 NE based cards at the
following addresses. It also states in which order they should be found and the
device they should be assigned.
Most ISA modules can take multiple comma separated I/O values. For example:
________________________________________________
| |
| alias eth0 3c501 |
| alias eth1 3c501 |
| options eth0 -o 3c501-0 io=0x280 irq=5|
| options eth1 -o 3c501-1 io=0x300 irq=7|
|________________________________________________|
The -o option allows for a unique name to be assigned to each module. The
reason for this is that you can not have two copies of the same module loaded.
The irq= option is used to specify the hardware IRQ, and the io= to specify the
different io ports.
By default, the Linux kernel only probes for one Ethernet device. You need to
pass command line arguments to the kernel in order to force detection of furter
boards.
To learn how furthere your ethernet card(s) work under Linux, you should refer
to the Ethernet-HOWTO.
-------------------------------------------------------------------------------
Chapter 7. IP Related Information
This section covers information specific to IP.
-------------------------------------------------------------------------------
7.1. Kernel Level Options
This section includes information on setting IP options within the kernel at
boot time. An example of these options are ip_forward or ip_bootp_agent. These
options are used by setting the value to a file in the
_____________________
| |
| /proc/sys/net/ipv4/|
|_____________________|
directory. The name of the file is the name of the command.
For example, to set ip_forward enabled, you would type
________________________________________
| |
| echo 1 > /proc/sys/net/ipv4/ip_forward|
|________________________________________|
-------------------------------------------------------------------------------
7.1.1. General IP option listing
* ip_forward
If ip_forward is set to 0 it is disabled. If it is sforwardany other number
it is enabled. This option is used in conjunction with technologies such as
routing between interfaces with IP Masquerading. .
* ip_default_ttl
This is the time to live for an IP Packet. The default is 64 milliseconds.
* ip_addrmask_agent - BOOLEAN
Reply to ICMP ADDRESS MASK requests. default TRUE (router) FALSE (host)
* ip_bootp_agent
- BOOLEAN Accept packets with source address of sort 0.b.c.d and destined to
this host, broadcast or multicast. Such packets are silently ignored
otherwise. default FALSE
* ip_no_pmtu_disc
- BOOLEAN Disable Path MTU Discovery. default FALSE
* ip_fib_model - INTEGER
0 - (DEFAULT) Standard model. All routes are in class MAIN. 1 - default
routes go to class DEFAULT. This mode should be very convenient for small
ISPs making policy routing. 2 - RFC1812 compliant model. Interface routes are
in class MAIN. Gateway routes are in class DEFAULT.
-------------------------------------------------------------------------------
7.2. EQL - multiple line traffic equaliser
The EQL device name is `eql'. With the standard kernel source, you may have
only one EQL device per machine. EQL provides a means of utilizing multiple
Point-to-Point lines such as PPP, slip, or plip as a single logical link to
carry tcp/ip. Often it is cheaper to use multiple lower speed lines than to
have one high speed line installed.
Kernel Compile Options:
_________________________________________________
|Network device support ---> |
| [*] Network device support |
| ____<*>_EQL_(serial_line_load_balancing)_support|
To support this mechanism, the machine at the other end of the lines must also
support EQL. Linux, Livingstone Portmasters and newer dial-in servers support
compatible facilities.
To configure EQL you will need the eql tools which are available from:
metalab.unc.edu.
Configuration is fairly straightforward. You start by configuring the eql
interface. The eql interface is just like any other network device. You
configure the IP address and mtu using the ifconfig utility. Here is an
example:
________________________________________
|root#_ifconfig_eql_192.168.10.1_mtu_1006|
Next, you need to manually initiate each of the lines you will use. These may
be any combination of Point-to-Point network devices. How you initiate the
connections will depend on what sort of link they are. Refer to the appropriate
sections for further information.
Lastly you need to associate the serial link with the EQL device. This is
called `enslaving' : it is done with the eql_enslave command as shown:
_________________________________
|root# eql_enslave eql sl0 28800 |
| root#_eql_enslave_eql_ppp0_14400|
The `estimated speed' parameter you supply eql_enslave doesn't do anything
directly. It is used by the EQL driver to determine what share of the datagrams
that device should receive. You can then fine tune the balancing of the lines
by playing with this value.
To disassociate a line from an EQL device, use the eql_emancipate command as
shown:
____________________________
|root#_eql_emancipate_eql_sl0|
You add routing as you would for any other Point-to-Point link, except that
your routes should refer to the eql device rather than the actual serial
devices. You would typically use:
____________________________
|root#_route_addthemselveseql|
The EQL driver was developed by Simon Janes simon@ncm.com.
Was_this_section_helpful?_Why_not_Donate_$2.50?
-------------------------------------------------------------------------------
7.3. IP Accounting (for Linux-2.0)
The IP accounting features of the Linux kernel allow you to collect and analyze
some network usage data. The data collected comprises the number of packets and
the number of bytes accumulated since the figures were last reset. You may
specify a variety of rules to categorize the figures to suit your purpose. This
option has been removed in kernel 2.1.102 because the old ipfwadm-based
firewalling was replaced by ``ipfwchains''.
Kernel Compile Options:
________________________
|Networking options --->|
| ____[*]_IP:_accounting_|
After you have compiled and installed the kernel, you need to use the ipfwadm
command to configure IP accounting. There are many different ways of breaking
down the accounting information. I've picked a simple example of what might be
useful. You should read the ipfwadm man page for more information.
Scenario: You have a ethernet network that is linked to the Internet via a PPP
link. On the ethernet, you have a machine that offers a number of services. You
are interested in knowing how much traffic is generated by each of ftp (and
world wide web traffic), as well as total tcp and udp traffic.
You might use a command set that looks like the following (shown as a shell
script):
_______________________________________________
|#!/bin/sh |
| # |
| # Flush the accounting rules |
| ipfwadm -A -f |
| # |
| # Set shortcuts |
| localnet=44.136.8.96/29 |
| any=0/0 |
| # Add rules for local ethernet segment |
| ipfwadm -A in -a -P tcp -D $localnet ftp-data|
| ipfwadm -A out -a -P tcp -S $localnet ftp-data|
| ipfwadm -A in -a -P tcp -D $localnet www |
| ipfwadm -A out -a -P tcp -S $localnet www |
| ipfwadm -A in -a -P tcp -D $localnet |
| ipfwadm -A out -a -P tcp -S $localnet |
| ipfwadm -A in -a -P udp -D $localnet |
| ipfwadm -A out -a -P udp -S $localnet |
| # |
| # Rules for default |
| ipfwadm -A in -a -P tcp -D $any ftp-data |
| ipfwadm -A out -a -P tcp -S $any ftp-data |
| ipfwadm -A in -a -P tcp -D $any www |
| ipfwadm -A out -a -P tcp -S $any www |
| ipfwadm -A in -a -P tcp -D $any |
| ipfwadm -A out -a -P tcp -S $any |
| ipfwadm -A in -a -P udp -D $any |
| ipfwadm -A out -a -P udp -S $any |
| # |
| # List the rules |
| ipfwadm -A -l -n |
| #_____________________________________________|
The names ``ftp-data'' and ``www'' refer to lines in /etc/services. The last
command lists each of the Accounting rules and displays the collected totals.
An important point to note when analyzing IP accounting is that totals for all
rules that match will be incremented. To obtain differential figures, you need
to perform appropriate maths. For example, if I wanted to know how much data
was not ftp or www, I would subtract the individual totals from the rule that
matches all ports.
________________________________________________________________________
| |
| root# ipfwadm -A -l -n |
| IP accounting rules |
| pkts bytes dir prot source destination ports |
| 0 0 in tcp 0.0.0.0/0 44.136.8.96/29 * -> 20|
| 0 0 out tcp 44.136.8.96/29 0.0.0.0/0 20 -> *|
| 10 1166 in tcp 0.0.0.0/0 44.136.8.96/29 * -> 80|
| 10 572 out tcp 44.136.8.96/29 0.0.0.0/0 80 -> *|
| 252 10943 in tcp 0.0.0.0/0 44.136.8.96/29 * -> * |
| 231 18831 out tcp 44.136.8.96/29 0.0.0.0/0 * -> *|
| 0 0 in udp 0.0.0.0/0 44.136.8.96/29 * -> * |
| 0 0 out undp 44.136.8.96/29 0.0.0.0/0 * -> *|
| 0 0 in tcp 0.0.0.0/0 0.0.0.0/0 * -> 20|
| 0 0 out tcp 0.0.0.0/0 0.0.0.0/0 20 -> *|
| 10 1166 in tcp 0.0.0.0/0 0.0.0.0/0 * -> 80|
| 10 572 out tcp 0.0.0.0/0 0.0.0.0/0 80 -> *|
| 253 10983 in tcp 0.0.0.0/0 0.0.0.0/0 * -> * |
| 231 18831 out tcp 0.0.0.0/0 0.0.0.0/0 * -> * |
| 0 0 in udp 0.0.0.0/0 0.0.0.0/0 * -> * |
| 0 0 out udp 0.0.0.0/0 0.0.0.0/0 * -> * |
|________________________________________________________________________|
-------------------------------------------------------------------------------
7.3.1. IP Accounting (for Linux-2.2)
The new accounting code is accessed via ``IP Firewall Chains''. See the_IP
chains_home_page for more information. You'll now need to use ipchains instead
of ipfwadm to configure your filters. (From Documentation/Changes in the latest
kernel sources).
-------------------------------------------------------------------------------
7.4. IP Aliasing
There are some applications where being able to configure multiple IP addresses
to a single network device is useful. Internet Service Providers often use this
facility to provide a "customized" feature to their World Wide Web and ftp
offerings for their customers. You can refer to the ``IP-Alias mini-HOWTO'' for
more information.
Kernel Compile Options:
_____________________________
|Networking options ---> |
| .... |
| [*] Network aliasing |
| .... |
| ____<*>_IP:_aliasing_support|
After compiling and installing your kernel with IP_Alias support, configuration
is very simple. The aliases are added to virtual network devices associated
with the actual network device. A simple naming convention applies to these
devices being <devname>:<virtual dev num>, e.g. eth0:0, ppp0:10 etc. Note that
the ifname:number device can only be configured after the main interface has
been set up.
For example, assume you have an ethernet network that supports two different IP
subnetworks simultaneously. You also wish your machine to have direct access to
both. You could use something like:
_______________________________________________________________
|root# ifconfig eth0 192.168.1.1 netmask 255.255.255.0 up |
| root# route add -net 192.168.1.0 netmask 255.255.255.0 eth0 |
| root# ifconfig eth0:0 192.168.10.1 netmask 255.255.255.0 up |
| root#_route_add_-net_192.168.10.0_netmask_255.255.255.0_eth0:0|
To delete an alias, add a `-' to the end of its name, then refer to it. It is
as simple as:
________________________
|root#_ifconfig_eth0:0-_0|
All routes associated with that alias will also be deleted automatically. Was
this_section_helpful?_Why_not_Donate_$2.50?
-------------------------------------------------------------------------------
7.5. IP Firewall (for Linux-2.0)
IP Firewall and Firewalling issues are covered in more depth in the Firewall-
HOWTO. IP Firewalling allows you to secure your machine against unauthorized
network access by filtering or allowing datagrams from or to IP addresses that
you nominate. There are three different classes of rules; incoming filtering,
outgoing filtering, and forwarding filtering. Incoming rules are applied to
datagrams that are received by a network device. Outgoing rules are applied to
datagrams that are to be transmitted by a network device. Forwarding rules are
applied to datagrams that are received and are not for this machine (ie.
datagrams that would be routed).
Kernel Compile Options:
____________________________________
|Networking options ---> |
| [*] Network firewalls |
| .... |
| [*] IP: forwarding/gatewaying |
| .... |
| [*] IP: firewalling |
| ____[_]_IP:_firewall_packet_logging|
Configuration of the IP firewall rules is performed using the ipfwadm command.
As I mentioned earlier, I am not a security expert. I will present an example
you can use. You should, however, do your own research and develop your own
rules.
Using your linux machine as a router and firewall gateway to protect your local
network from unauthorized access (from outside your network) is probably the
most common use of an IP firewall.
The following configuration is based on a contribution from Arnt Gulbrandsen:
<agulbra@troll.no>.
The example describes the configuration of the firewall rules on the Linux
firewall/router machine illustrated below:
________________________________________________________
| |
| - - |
| \ | 172.16.37.0 |
| \ | /255.255.255.0|
| \ --------- | |
| | 172.16.174.30 | Linux | | |
| NET =================| f/w |------| ..37.19 |
| | PPP | router| | -------- |
| / --------- |--| Mail | |
| / | | /DNS | |
| / | -------- |
| - - |
|________________________________________________________|
The following commands would normally be placed in an rc file. They would be
automatically started each time the system boots. For maximum security, they
would be performed after the network interfaces are configured (but before the
interfaces are actually brought up) to prevent anyone gaining access while the
firewall machine is rebooting.
______________________________________________________________________
|#!/bin/sh |
| # Flush the 'Forwarding' rules table |
| # Change the default policy to 'accept' |
| # |
| /sbin/ipfwadm -F -f |
| /sbin/ipfwadm -F -p accept |
| # |
| # .. and for 'Incoming' |
| # |
| /sbin/ipfwadm -I -f |
| /sbin/ipfwadm -I -p accept |
| # First off, seal off the PPP interface |
| # I'd love to use '-a deny' instead of '-a reject -y' but then it |
| # would be impossible to originate connections on that interface too.|
| # The -o causes all rejected datagrams to be logged. This trades |
| # disk space against knowledge of an attack of configuration error. |
| # |
| /sbin/ipfwadm -I -a reject -y -o -P tcp -S 0/0 -D 172.16.174.30 |
| # Throw away certain kinds of obviously forged packets right away: |
| # Nothing should come from multicast/anycast/broadcast addresses |
| # |
| /sbin/ipfwadm -F -a deny -o -S 224.0/3 -D 172.16.37.0/24 |
| # |
| # and nothing coming from the loopback network should ever be |
| # seen on a wire |
| # |
| /sbin/ipfwadm -F -a deny -o -S 127.0/8 -D 172.16.37.0/24 |
| # accept incoming SMTP and DNS connections, but only |
| # to the Mail/Name Server |
| # |
| /sbin/ipfwadm -F -a accept -P tcp -S 0/0 -D 172.16.37.19 25 53 |
| # |
| # DNS uses UDP as well as TCP, so allow that too |
| # for questions to our name server |
| # |
| /sbin/ipfwadm -F -a accept -P udp -S 0/0 -D 172.16.37.19 53 |
| # |
| # but not "answers" coming to dangerous ports like NFS and |
| # Larry McVoy's NFS extension. If you run squid, add its port here. |
| # |
| /sbin/ipfwadm -F -a deny -o -P udp -S 0/0 53 \ |
| -D 172.16.37.0/24 2049 2050 |
| # answers to other user ports are okay |
| # |
| /sbin/ipfwadm -F -a accept -P udp -S 0/0 53 \ |
| -D 172.16.37.0/24 53 1024:65535 |
| # Reject incoming connections to identd |
| # We use 'reject' here so that the connecting host is told |
| # straight away not to bother continuing, otherwise we'd experience |
| # delays while ident timed out. |
| # |
| /sbin/ipfwadm -F -a reject -o -P tcp -S 0/0 -D 172.16.37.0/24 113 |
| # Accept some common service connections from the 192.168.64 and |
| # 192.168.65 networks, they are friends that we trust. |
| # |
| /sbin/ipfwadm -F -a accept -P tcp -S 192.168.64.0/23 \ |
| -D 172.16.37.0/24 20:23 |
| # accept and pass through anything originating inside |
| # |
| /sbin/ipfwadm -F -a accept -P tcp -S 172.16.37.0/24 -D 0/0 |
| # deny most other incoming TCP connections and log them |
| # (append 1:1023 if you have problems with ftp not working) |
| # |
| /sbin/ipfwadm -F -a deny -o -y -P tcp -S 0/0 -D 172.16.37.0/24 |
| # ... for UDP too |
| # |
| /sbin/ipfwadm_-F_-a_deny_-o_-P_udp_-S_0/0_-D_172.16.37.0/24__________|
Good firewall configurations are a little tricky. This example should be a
reasonable starting point for you. The ipfwadm manual page offers some
assistance in how to use the tool. If you intend to configure a firewall, be
sure to ask around and get as much advice from sources you consider reliable.
Get someone to test/sanity check your configuration from the outside.
-------------------------------------------------------------------------------
7.5.1. IP Firewall (for Linux-2.2)
The new firewalling code is accessed via ``IP Firewall Chains''. See the_IP
chanins_home_page for more information. Among other things, you'll now need to
use ipchains instead of ipfwadm to configure your filters (From Documentation/
Changes in the latest kernel sources).
We are aware that this is a sorely out of date statement. We are currently
working on getting this section current. You can expect a newer version
sometime this year.
-------------------------------------------------------------------------------
7.6. IPIP Encapsulation
Why would you want to encapsulate IP datagrams within IP datagrams? It must
seem odd if you've never seen a working application. Two common places where it
is used are in Mobile-IP and IP-Multicast. Amateur Radio is perhaps the most
widely spread (and least known) useage.
Kernel Compile Options:
__________________________________
|Networking options ---> |
| [*] TCP/IP networking |
| [*] IP: forwarding/gatewaying|
| .... |
| ____<*>_IP:_tunneling____________|
IP tunnel devices are called `tunl0', `tunl1' etc.
"But why ?". Ok, ok. Conventional IP routing rules mandate that an IP network
comprises a network address and a network mask. This produces a series of
contiguous addresses that may all be routed via a single routing entry. This is
very convenient. It means that you may use any particular IP address while you
are connected to its piece of the network. In most instances this is ok. If you
are a mobile netizen, however, then you may not be able to stay connected to
the one place all the time. IP/IP encapsulation (IP tunneling) allows you to
overcome this restriction by allowing datagrams destined for your IP address to
be wrapped up and redirected to another IP address. If you know that you're
going to be operating from another IP network, you can set up a machine on your
home network to accept datagrams to your IP address. You can then redirect
these datagrams to the address that you will be temporarily using.
-------------------------------------------------------------------------------
7.6.1. A tunneled network configuration.
_____________________________________________________
| |
| 192.168.1/24 192.168.2/24|
| - - |
| | ppp0 = ppp0 = | |
| | aaa.bbb.ccc.ddd fff.ggg.hhh.iii | |
| | | |
| | /-----\ /-----\ | |
| | | | // | | | |
| |---| A |------//---------| B |---| |
| | | | // | | | |
| | \-----/ \-----/ | |
| | | |
| - - |
|_____________________________________________________|
The diagram illustrates another possible reason to use IPIP encapsulation;
virtual private networking. This example presupposes that you have two
machines, each with a simple dial up Internet connection. Each host is
allocated just a single IP address. Behind each of these machines are some
private local area networks. These LANs are configured with reserved IP network
addresses. Suppose that you want to allow any host on network A to connect to
any host on network B (just as if they were properly connected to the Internet
with a network route). IPIP encapsulation will allow you to do this
configuration. Note: encapsulation does not solve the problem of how you get
the hosts on networks A and B to talk to any other on the Internet. You will
still need to use tricks like IP Masquerade. Encapsulation is normally
performed by machines functioning as routers.
Linux router `A' would be configured with a script like the following:
____________________________________________________________
|#!/bin/sh |
| PATH=/sbin:/usr/sbin |
| mask=255.255.255.0 |
| remotegw=fff.ggg.hhh.iii |
| # |
| # Ethernet configuration |
| ifconfig eth0 192.168.1.1 netmask $mask up |
| route add -net 192.168.1.0 netmask $mask eth0 |
| # |
| # ppp0 configuration (start ppp link, set default route) |
| pppd |
| route add default ppp0 |
| # |
| # Tunnel device configuration |
| ifconfig tunl0 192.168.1.1 up |
| route_add_-net_192.168.2.0_netmask_$mask_gw_$remotegw_tunl0|
Linux router `B' would be configured with a similar script:
____________________________________________________________
|#!/bin/sh |
| PATH=/sbin:/usr/sbin |
| mask=255.255.255.0 |
| remotegw=aaa.bbb.ccc.ddd |
| # |
| # Ethernet configuration |
| ifconfig eth0 192.168.2.1 netmask $mask up |
| route add -net 192.168.2.0 netmask $mask eth0 |
| # |
| # ppp0 configuration (start ppp link, set default route) |
| pppd |
| route add default ppp0 |
| # |
| # Tunnel device configuration |
| ifconfig tunl0 192.168.2.1 up |
| route_add_-net_192.168.1.0_netmask_$mask_gw_$remotegw_tunl0|
The command:
___________________________________________________________
|route_add_-net_192.168.1.0_netmask_$mask_gw_$remotegw_tunl0|
reads: `Send any datagrams destined for 192.168.1.0/24 inside an IPIP encap
datagram with a destination address of aaa.bbb.ccc.ddd'.
Note that the configurations are reciprocated at either end. The tunnel device
uses the `gw' in the route as the destination of the IP datagram (where it will
place the datagram it has received to route). That machine must know how to
decapsulate IPIP datagrams. In other words, it must also be configured with a
tunnel device.
-------------------------------------------------------------------------------
7.6.2. A tunneled host configuration.
You do not have to be routing a whole network. You could, for example, route
just a single IP address. In that instance you might configure the tunl device
on the `remote' machine with its home IP address. At the A end would have a
host route (and Proxy Arp) rather than a network route via the tunnel device.
Let's redraw and modify our configuration appropriately. Now we have just host
`B' which you want to act and behave as if it is both fully connected to the
Internet, and also part of the remote network supported by host `A':
________________________________________________
| |
| 192.168.1/24 |
| - |
| | ppp0 = ppp0 = |
| | aaa.bbb.ccc.ddd fff.ggg.hhh.iii |
| | |
| | /-----\ /-----\ |
| | | | // | | |
| |---| A |------//---------| B | |
| | | | // | | |
| | \-----/ \-----/ |
| | also: 192.168.1.12|
| - |
|________________________________________________|
Linux router `A' would be configured with:
_________________________________________________________
|#!/bin/sh |
| PATH=/sbin:/usr/sbin |
| mask=255.255.255.0 |
| remotegw=fff.ggg.hhh.iii |
| # |
| # Ethernet configuration |
| ifconfig eth0 192.168.1.1 netmask $mask up |
| route add -net 192.168.1.0 netmask $mask eth0 |
| # |
| # ppp0 configuration (start ppp link, set default route)|
| pppd |
| route add default ppp0 |
| # |
| # Tunnel device configuration |
| ifconfig tunl0 192.168.1.1 up |
| route add -host 192.168.1.12 gw $remotegw tunl0 |
| # |
| # Proxy ARP for the remote host |
| arp_-s_192.168.1.12_xx:xx:xx:xx:xx:xx_pub_______________|
Linux host `B' would be configured with:
___________________________________________________________
|#!/bin/sh |
| PATH=/sbin:/usr/sbin |
| mask=255.255.255.0 |
| remotegw=aaa.bbb.ccc.ddd |
| # |
| # ppp0 configuration (start ppp link, set default route) |
| pppd |
| route add default ppp0 |
| # |
| # Tunnel device configuration |
| ifconfig tunl0 192.168.1.12 up |
| route_add_-net_192.168.1.0_netmask_$mask_gw_$remotegwtunl0|
This sort of configuration is more typical of a Mobile-IP application: a single
host wants to roam around the Internet and maintain a single usable IP address
the whole time. You should refer to the Mobile-IP section for more information
on how this is handled in practice.
-------------------------------------------------------------------------------
7.7. IP Masquerade
Many people have a simple dialup account to connect to the Internet. Nearly
everybody using this sort of configuration is allocated a single IP address by
the Internet Service Provider. This is normally enough to allow only one host
full access to the network. IP Masquerade is a clever trick that enables you to
have many machines make use of that one IP address. It causes the other hosts
to look like the machine supporting the dial-up connection. This is where the
term masquerade applies. There is a small caveat: the masquerade function
usually works only in one direction. That is, the masqueraded hosts can make
calls out, but they cannot accept or receive network connections from remote
hosts. This means that some network services do not work (such as talk), and
others (such as ftp) must be configured in passive (PASV) mode to operate.
Fortunately, the most common network services such as telnet, World Wide Web
and irc work just fine.
Kernel Compile Options:
______________________________________________________________
|Code maturity level options ---> |
| [*] Prompt for development and/or incomplete code/drivers|
| Networking options ---> |
| [*] Network firewalls |
| .... |
| [*] TCP/IP networking |
| [*] IP: forwarding/gatewaying |
| .... |
| ____[*]_IP:_masquerading_(EXPERIMENTAL)______________________|
Normally, you have your linux machine supporting a SLIP or PPP dial-up line
(just as it would if it were a standalone machine). Additionally, it would have
another network device configured (perhaps an ethernet) with one of the
reserved network addresses. The hosts to be masqueraded would be on this second
network. Each of these hosts would have the IP address of the ethernet port of
the linux machine set as their default gateway or router.
A typical configuration might look something like this:
________________________________________________________
| |
| - - |
| \ | 192.168.1.0 |
| \ | /255.255.255.0|
| \ --------- | |
| | | Linux | .1.1 | |
| NET =================| masq |------| |
| | PPP/slip | router| | -------- |
| / --------- |--| host | |
| / | | | |
| / | -------- |
| - - |
|________________________________________________________|
-------------------------------------------------------------------------------
7.7.1. Masquerading with IPFWADM (Kernels 2.0.x)
The most relevant commands for this configuration are:
_________________________________________________________________
|# Network route for ethernet |
| route add -net 192.168.1.0 netmask 255.255.255.0 eth0 |
| # |
| # Default route to the rest of the Internet. |
| route add default ppp0 |
| # |
| # Cause all hosts on the 192.168.1/24 network to be masqueraded.|
| ipfwadm_-F_-a_m_-S_192.168.1.0/24_-D_0.0.0.0/0__________________|
-------------------------------------------------------------------------------
7.7.2. Masquerading with IPCHAINS
This is similar to using IPFWADM, but the command structure has changed:
__________________________________________________________________________
| |
| # Network route for ethernet |
| route add -net 192.168.1.0 netmask 255.255.255.0 eth0 |
| # |
| # Default route to the rest of the Internet. |
| route add default ppp0 |
| # |
| # Cause all hosts on the 192.168.1/24 network to be masqueraded.|
| ipchains -A forward -s 192.168.1.0/24 -j MASQ |
|__________________________________________________________________________|
You can get more information on the Linux IP Masquerade feature from the IP
Masquerade_Resource_Page. Also, a very detailed document about masquerading is
the ``IP-Masquerade mini-HOWTO'' (which also intructs to configure other OS's
to run with a Linux masquerade server).
For information on Applications of IP Masquerading, check the IPMASQ
Applications page.
-------------------------------------------------------------------------------
7.8. IP Transparent Proxy
IP transparent proxy is a feature that enables you to redirect servers or
services destined for another machine to those services on this machine.
Typically, this would be useful where you have a linux machine as a router (and
also provides a proxy server). You would redirect all connections destined for
that service remotely to the local proxy server.
Kernel Compile Options:
___________________________________________________________
|Code maturity level options ---> |
| [*] Prompt for development and/or incomplete code/drivers|
| Networking options ---> |
| [*] Network firewalls |
| .... |
| [*] TCP/IP networking |
| .... |
| [*] IP: firewalling |
| .... |
| [*]_IP:_transparent_proxy_support_(EXPERIMENTAL)_________|
Configuration of the transparent proxy feature is performed using the ipfwadm
command.
An example that might be useful is as follows:
________________________________________________
|root#_ipfwadm_-I_-a_accept_-D_0/0_telnet_-r_2323|
This example will cause any connection attempts to port telnet (23) on any host
to be redirected to port 2323 on this host. If you run a service on that port,
you could forward telnet connections, log them, or do whatever fits your needs.
A more interesting example is redirecting all http traffic through a local
cache. However, the protocol used by proxy servers is different from native
http: (where a client connects to www.server.com:80 and asks for /path/page).
When it connects to the local cache, it contacts proxy.local.domain:8080 and
asks for www.server.com/path/page.
To filter an http request through the local proxy, you need to adapt the
protocol by inserting a small server, called transproxy (you can find it on the
world wide web). You can choose to run transproxy on port 8081.Just ssue this
command:
____________________________________________
|root#_ipfwadm_-I_-a_accept_-D_0/0_80_-r_8081|
The transproxy program, then, will receive all connections meant to reach
external servers, and will pass them to the local proxy (after fixing protocol
differences). Was_this_section_helpful?_Why_not_Donate_$2.50?
-------------------------------------------------------------------------------
7.9. IPv6
Just when you thought you were beginning to understand IP networking, the rules
get changed! IPv6 is the shorthand notation for version 6 of the Internet
Protocol. IPv6 was developed primarily to overcome the concerns in the Internet
community. Users worried that there would soon be a shortage of IP addresses to
allocate. IPv6 addresses are 16 bytes long (128 bits). IPv6 incorporates a
number of other changes, mostly simplifications, that will make IPv6 networks
more managable than IPv4 networks.
Linux already has a working (but not complete) IPv6 implementation in the 2.2.*
series kernels.
Was_this_section_helpful?_Why_not_Donate_$2.50?
-------------------------------------------------------------------------------
7.10. IPv6 Linux resources
IPv6-HOWTO
IPv6_for_Linux
Linux_IPv6_RPM_Project
IPv6_FAQ/HOWTO Was_this_section_helpful?_Why_not_Donate_$2.50?
-------------------------------------------------------------------------------
7.11. Mobile IP
The term "IP mobility" describes the ability of a host that is able to move its
network connection from one point on the Internet to another (without changing
its IP address or losing connectivity). Usually when an IP host changes its
point of connectivity, it must also change its IP address. IP Mobility
overcomes this problem by allocating a fixed IP address to the mobile host. It
also uses IP encapsulation (tunneling) with automatic routing to ensure that
datagrams destined for it are routed to the actual IP address it is currently
using.
A project is underway to provide a complete set of IP mobility tools for Linux.
The status of the project and tools may be obtained from: Linux_Mobile_IP_Home
Page. Was_this_section_helpful?_Why_not_Donate_$2.50?
-------------------------------------------------------------------------------
7.12. Multicast
IP Multicast allows an arbitrary number of IP hosts on disparate IP networks to
have IP datagrams simultaneously routed to them. This mechanism is exploited to
provide Internet wide "broadcast" material, such as audio and video
transmissions, as well as other novel applications.
Kernel Compile Options:
__________________________
| |
| Networking options --->|
| [*] TCP/IP networking |
| .... |
| [*] IP: multicasting |
|__________________________|
A suite of tools and some minor network configuration is required. Please check
the Multicast-HOWTO for more information on Multicast support in Linux.
Was_this_section_helpful?_Why_not_Donate_$2.50?
-------------------------------------------------------------------------------
7.13. Traffic Shaper - Changing allowed bandwidth
The traffic shaper is a driver that creates new interface devices. Those
devices are traffic-limited in a user-defined way. They rely on physical
network devices for actual transmission, and they can be used as outgoing
routed for network traffic.
The shaper was introduced in Linux-2.1.15, and it was backported to Linux-
2.0.36 (it appeared in 2.0.36-pre-patch-2 distributed by Alan Cox, the author
of the shaper device and maintainer of Linux-2.0).
The traffic shaper can only be compiled as a module. It is configured by the
shapecfg program. The commands are similar to the following:
_____________________________
|shapecfg attach shaper0 eth1 |
| shapecfg_speed_shaper0_64000|
The shaper device can only control the bandwidth of outgoing traffic (as
packets are transmitted via the shaper; only according to the routing tables).
A ``route by source address'' functionality could help in limiting the overall
bandwidth of specific hosts using a Linux router.
Linux-2.2 already has support for such routing. If you need it for Linux-2.0
please check the patch by Mike McLagan at ftp.invlogic.com. Refer to
Documentationnetworking/shaper.txt for further information about the shaper.
If you want to try out a (tentative) shaping for incoming packets, try out
rshaper-1.01 (or newer) from ftp.systemy.it. Was_this_section_helpful?_Why_not
Donate_$2.50?
-------------------------------------------------------------------------------
Chapter 8. DHCP and DHCPD
DHCP is an acronym for Dynamic Host Configuration Protocol. The creation of
DHCP has made configuring the network on multiple hosts extremely simple.
Instead of having to configure each host separately, you can assign all of the
common host-used parameters with a DHCP server.
Each time the host boots up, it will broadcast a packet to the network. This
packet is a call to any DHCP servers located on the same segment to configure
the host.
DHCP is extermely useful in assigning items such as the IP address, Netmask,
and gateway of each host.
-------------------------------------------------------------------------------
8.1. DHCP Client Setup for users of LinuxConf
When you are in linux, and you are logged in as the user "root", start the
program linuxconf. This program comes with all versions of redhat, and it works
with X as well as with the console. It also works for both SuSe and Caldera.
__________________________________________
| |
| Select Networking |
| ----------------->Basic Host Information|
| ----------------->Select Enable |
| ----------------->Set Config Mode DHCP |
|__________________________________________|
Was_this_section_helpful?_Why_not_Donate_$2.50?
-------------------------------------------------------------------------------
8.2. DHCP Server Setup for Linux
Retrieve DHCPD (if your machine does not already have it installed). Get_DHCPD
Quick Note: MAKE SURE YOU HAVE MULTICAST ENABLED IN THE KERNEL.
If there is not a binary distribution for your version of linux, then you will
have to compile DHCPD.
Edit your /etc/rc.d/rc.local to reflect an addition of a route for
255.255.255.255.
Quoted from DHCPd README:
In order for dhcpd to work correctly with picky DHCP clients (e.g., Windows
95), it must be able to send packets with an IP destination address of
255.255.255.255. Unfortunately, Linux insists on changing 255.255.255.255 into
the local subnet broadcast address (in this case, the address would be
192.5.5.223). This results in a DHCP protocol violation. While many DHCP
clients don't notice the problem, some (e.g., all Microsoft DHCP clients) will
recognize the violation. Clients that have this problem will appear not to see
DHCPOFFER messages from the server.
Type the following as root:
route add -host 255.255.255.255 dev eth0
If the message appears:
255.255.255.255: Unknown host
Try adding the following entry to your /etc/hosts file:
255.255.255.255 dhcp
Then, try:
route add -host dhcp dev eth0
-------------------------------------------------------------------------------
8.2.1. Options for DHCPD
Now you need to configure DHCPd. In order to do this, you will have to create
or edit /etc/dhcpd.conf. There is a graphical interface for dhcpd configuration
under linuxconf. This makes configuring and managing DHCPD extremely simple.
If you want to configure it by hand, you should follow instructions below. I
suggest configuring it by hand at least once. It will help in the diagnostics
that a GUI can't provide. Unfortunately Micrsoft doesn't believe this!
The simplest way to assign IP addresses is to assign them randomly. A sample
configuration file that shows this type of setup is displayed below:
______________________________________________________
| |
| # Sample /etc/dhcpd.conf |
| # (add your comments here) |
| default-lease-time 1200; |
| max-lease-time 9200; |
| option subnet-mask 255.255.255.0; |
| option broadcast-address 192.168.1.255; |
| option routers 192.168.1.254; |
| option domain-name-servers 192.168.1.1, 192.168.1.2;|
| option domain-name "mydomain.org"; |
| subnet 192.168.1.0 netmask 255.255.255.0 { |
| range 192.168.1.10 192.168.1.100; |
| range 192.168.1.150 192.168.1.200; |
| } |
|______________________________________________________|
This will allow the DHCP server to assign the client an IP address from the
range 192.168.1.10-192.168.1.100 or 192.168.1.150-192.168.1.200.
If the client doesn't request a longer time frame, then the DHCP server will
lease an IP address for 1200 seconds. Otherwise, the maximum (allowed) lease
the server will allow is 9200 seconds. The server sends the following
parameters to the client:
Use 255.255.255.0 as your subnet mask Use 192.168.1.255 as your broadcast
address Use 192.168.1.254 as your default gateway USE 192.168.1.1 and
192.168.1.2 as your DNS servers.
If you specify a WINS server for your Windows clients, you need to include the
following option in the dhcpd.conf file:
option netbios-name-servers 192.168.1.1;
You can also assign specific IP addresses based on the clients' ethernet MAC
address as follows:
___________________________________________
| |
| host haagen { |
| hardware ethernet 08:00:2b:4c:59:23;|
| fixed-address 192.168.1.222; |
| } |
|___________________________________________|
This will assign IP address 192.168.1.222 to a client with the ethernet MAC
address of 08:00:2b:4c:59:23.
-------------------------------------------------------------------------------
8.2.2. Starting the server
In most cases the DHCP installation doesn't create a "dhcpd.leases" file.
Before you start the server, you must create an empty file:
touch /var/state/dhcp/dhcpd.leases
To start the DHCP server, simply type (or include in the bootup scripts):
/usr/sbin/dhcpd
This will start dhcpd on eth0 device. If you need to start it on another
device, simply supply it on the command line as shown below:
/usr/sbin/dhcpd eth1
If you wish to test the configuration for any oddities, you can start dhcpd
with the debugging mode. Typing the command below will allow you to see exactly
what is going on with the server.
/usr/sbin/dhcpd -d -f
Boot up a client.Take a look at the console of the server. You will see a
number of debugging messages appear on the screen.
Your done
-------------------------------------------------------------------------------
Chapter 9. Advanced Networking with Kernel 2.2
Kernel 2.2 has advanced the routing capabilities of Linux quite a bit.
Unfortunately, the documentation for using these new capabilities is almost
impossible to find (even if it does exist).
I have put some time into it and have been able to do a little with it. I will
add more as I have the time and the assistance to figure out what it all means.
In kernel 2.0 and below, Linux used the standard route command to place routes
in a single routing table. If you were to type netstat -rn at the Linux prompt,
you would see and example.
In the newer kernels (2.1 and above), you have another option. This option is
rule based, and it allows you to have multiple routing tables. The new rules
allow a great deal of flexibility in deciding how a packet is handled. You can
choose between routes based not only on the destination address, but also on
the source address, TOS, or incoming device.
-------------------------------------------------------------------------------
9.1. The Basics
Listing the Routing Table:
ip route
Now on my machine, this equates to the following output:
_______________________________________________________________________
| |
| 207.149.43.62 dev eth0 scope link |
| 207.149.43.0/24 dev eth0 proto kernel scope link src 207.149.43.62|
| default via 207.149.43.1 dev eth0 |
|_______________________________________________________________________|
The first line:
207.149.43.62 dev eth0 scope link is the route for the interface
The second line:
207.149.43.0/24 dev eth0 proto kernel scope link src 207.149.43.62 Is the route
that says everything that goes to 207.149.43.0 needs to go out 207.149.43.62.
The third line:
default via 207.149.43.1 dev eth0 is the default route.
-------------------------------------------------------------------------------
9.1.1. Using the information
Now that we have walked through a basic routing table, lets see how we use it.
First read the_Policy_routing_text. If you get confused, don't worry -- it is a
confusing text. It will give you the run down on everything that the new
routing code can accomplish.
-------------------------------------------------------------------------------
9.2. Adding a route with the new ip tools
In the previous section, we spoke about both listing the routing table and we
discussed what the basics of that listing meant. Fortunately, the output is
very similar to the syntax that you would use to implement that exact routing
table on your own.
___________________________________________________________________
| |
| ip route add 207.149.43.62 dev eth0 scope link |
| ip route add 207.149.43.0/24 dev eth0 proto kernel scope link src|
| 207.149.43.62 |
| ip route add 127.0.0.0/8 dev lo scope link |
| ip route add default via 207.149.43.1 dev eth0 |
|___________________________________________________________________|
As you can see, the output and input are almost exact (except for the adding of
the ip route add in front of the line).
Note: We are aware that the documentation on Routing with 2.2 is sorely lacking
in details. In fact, I think EVERYONE is aware of it! If you have any
experience in this matter, please contact us at: poet@linuxports.com We would
like to get any information that you may have to help strengthen our
documentation!
Was_this_section_helpful?_Why_not_Donate_$2.50?
-------------------------------------------------------------------------------
9.3. Using NAT with Kernel 2.2
The IP Network Address Translation facility is pretty much the standardized
"big brother" of the Linux IP Masquerade facility. It is specified in some
detail in RFC-1631 (at your nearest RFC archive). NAT provides features that
IP-Masquerade does not (which make it eminently more suitable for use in both
corporate firewall router designs, and in larger scale installations).
An alpha implementation of NAT for Linux 2.0.29 kernel has been developed by
Michael.Hasenstein: Michael.Hasenstein@informatik.tu-chemnitz.de. Michael's
documentation and implementation are available from:
Linux_IP_Network_Address_Web_Page
The much improved TCP/IP stack of Linux 2.2 kernel has NAT functionality built-
in. This facility seems to render the work by Michael Hasenstein somewhat
obsolete (Michael.Hasenstein@informatik.tu-chemnitz.de).
To get it to work, you need the kernel with enabled CONFIG_IP_ADVANCED_ROUTER,
CONFIG_IP_MULTIPLE_TABLES (aka policy routing) and CONFIG_IP_ROUTE_NAT (aka
fast NAT). And if you want to use finer grained NAT rules, you may also want to
turn on firewalling (CONFIG_IP_FIREWALL) and CONFIG_IP_ROUTE_FWMARK. To
actually operate these kernel features, you will need the "ip" program by
Alexey Kuznyetsov from ftp://ftp.inr.ac.ru/ip-routing/.
Incoming datagrams NAT
Now, to translate addresses of incoming datagrams, the following command is
used:
_________________________________________________________
|___ip_route_add_nat_<ext-addr>[/<masklen>]_via_<int-addr>|
This will make an incoming packet destined to "ext-addr" (the address visible
from outside Internet) to have its destination address field rewritten to "int-
addr" (the address in your internal network, behind your gateway/firewall). The
packet is then routed according to the local routing table. You can translate
either single host addresses or complete blocks. Examples:
________________________________________________________
| |
| ip route add nat 195.113.148.34 via 192.168.0.2 |
| ip route add nat 195.113.148.32/27 via 192.168.0.0|
|________________________________________________________|
First command will make internal address 192.168.0.2 accessible as
195.113.148.34. The second example shows remapping block 192.168.0.0-31 to
195.113.148.32-63. Was_this_section_helpful?_Why_not_Donate_$2.50?
-------------------------------------------------------------------------------
Chapter 10. Kernel 2.2 IP Command Reference (Work In Progress)
10.1. ip
If you have the iproute2 tools installed, then executing the ip command will
allow the basic syntax to be displayed.
_____________________________________________________________________________
| |
| [root@jd Net4]# ip |
| Usage: ip [ OPTIONS ] OBJECT { COMMAND | help } |
| where OBJECT := { link | addr | route | rule | neigh | tunnel | |
| maddr | mroute | monitor } |
| OPTIONS := { -V[ersion] | -s[tatistics] | -r[esolve] | |
| -f[amily] { inet | inet6 | dnet | link } | -o[neline] }|
|_____________________________________________________________________________|
There are also several options available:
-V, -Version -- print the version of the ip utility you are using and exit.
-s, -stats, -statistics -- obtain more output on the speficied device. You can
issue this option more than once to increase the amount of information being
displayed.
-f, -family followed by a protocol family identifier such as: inet, inet6 or
link. -- Specify the exact protocol family to use. Inet uses the standard IPv4
(e.g.; current Internet standard), inet6 uses IPv6 (ground breadking, never to
be implemented Internet standard), and link (a physical link). If you do not
present the option, the protocol family is guessed. If not enough information
is present, it will fallback to the default setting.
-o, -oneline Show the output each device record in a single line.
-r, -resolve Use the system resolver (e.g.; DNS) to print actual names (versus
IP numbers).
OBJECT Is the object (device) that you can retrieve information from, and/or
you can also manage the device. The current device types understood by the
current implementation are:
* link -- The network device e.g.; eth0 or ppp0 .
* address -- The IP (IP or IPv6) address on the specified device.
* neigh -- The ARP or NDISC cache entry.
* route -- The routing table entry.
* rule -- The rule in routing policy database.
* maddress -- The multicast address.
* mroute -- The multicast route cache entry.
* tunnel -- Whether or not to tunnel over IP.
The amount of possible options allowed on each object type depend on the type
of action being taken. As a basic rule, it is possible to add, delete, or to
show the object(s). Not all object will allow additional commands to be used.
Of course, command help is available for all objects. When help is used, it
will print out a list of available sytanx conventions for the given object.
If you do not give a command, the default command will be assumed. Typically
the default command is to list the objects. If the objects can not be listed,
the default will provide standard help output.
ARGUMENTS is the list of arguments that can be passed to the command. The
number of arguments depends upon both the command and the object being used.
There are two types of arguments:
Flags consist of a keyword followed by a value. For convenience, each command
contains some default parameters that can be left out for easier use. For
example, the parameter dev> defaults to an ip link.
Mistakes... thank God for smart coders! All the operations within the ip
commands are dynamic. If the sytanx of the ip utility fails, it will not change
the configuration of the system. There is an exception to this rule: the ip
link command. This command is used to change part of a devices parameters.
It is difficult to list all the error messages (especially the syntax errors).
Generally speaking, their meaning is clear in the context of the commands. The
most common mistakes are: 1. Netlink is not configured in the kernel. The
message is: Cannot open netlink socket: Invalid value
2. RTNETLINK is not configured in the kernel. One of the following messages may
be printed (depending upon the command): Cannot talk to rtnetlink: Connection
refused Cannot send dump request: Connection refused
3. Option CONFIG_IP_MULTIPLE_TABLES was not selected when configuring kernel.
In this case, any attempt to use commandip rule will fail. For example:
jd@home $ ip rule list RTNETLINK error: Invalid argument dump terminated Was
this_section_helpful?_Why_not_Donate_$2.50?
-------------------------------------------------------------------------------
Chapter 11. Using common PC hardware
11.1. ISDN
The Integrated Services Digital Network (ISDN) is a series of standards that
specify a general purpose switched digital data network. An ISDN `call' creates
a synchronous Point-to-Point data service to the destination. ISDN is generally
delivered on a high speed link that is broken down into a number of discrete
channels. There are two different types of channels, the `B Channels' (which
will actually carry the user data) and a single channel called the `D channel'
(which is used to send control information to the ISDN exchange: used for
establishing calls and other functions). In Australia, for example, ISDN may be
delivered on a 2Mbps link that is broken into 30 discrete 64kbps B channels
(with one 64kbps D channel). Any number of channels may be used at a time, and
these channels can be used in any combination. You could, for example,
establish 30 separate calls to 30 different destinations at 64kbps each. You
could also establish 15 calls to 15 different destinations at 128kbps each (two
channels used per call). Finally, you could establish just a small number of
calls while leaving the rest idle. A channel may be used for either incoming or
outgoing calls. The original intention of ISDN was to allow Telecommunications
companies to provide a single data service. This service could deliver either
telephone (via digitised voice) or data services to your home or business. In
this case, the customer would not be required to make any special configuration
changes.
There are a few different ways to connect your computer to an ISDN service. One
way is to use a device called a `Terminal Adaptor' .This adaptor plugs into the
Network Terminating Unit (that you telecommunications carrier will have
installed when you received your ISDN service), and it presents a number of
serial interfaces. One of those interfaces is used to enter commands. Some
commands are used to establish calls and configuration, while others are
actually connected to the network devices that are to use the data circuits
(when they are established). Linux will work in this sort of configuration
without modification: you just treat the port on the Terminal Adaptor like you
would treat any other serial device. The kernel ISDN support is also designed
to allow the user to install an ISDN card into the Linux machine. This allows
the Linux software to handle the protocols, and the software can make the calls
itself.
Kernel Compile Options:
_______________________________________
|ISDN subsystem ---> |
| <*> ISDN support |
| [ ] Support synchronous PPP |
| [ ] Support audio via ISDN |
| < > ICN 2B and 4B support |
| < > PCBIT-D support |
| <_>_Teles/NICCY1016PC/Creatix_support|
The Linux implementation of ISDN supports a number of different types of
internal ISDN cards. These are listed in the kernel configuration options:
* ICN 2B and 4B
* Octal PCBIT-D
* Teles ISDN-cards and compatibles
Some of these cards require software to be downloaded to make them operational.
A separate utility exists to allow downloading to happen.
Full details on how to configure the Linux ISDN support is available from the /
usr/src/linux/Documentation/isdn/ directory. You can also check the FAQ
dedicated to isdn4linux: it is available at www.lrz-muenchen.de. (You can click
on the english flag to get an english version).
A note about PPP. The PPP suite of protocols will operate over either
asynchronous or synchronous serial lines. The commonly distributed PPP daemon
for Linux `pppd' supports only asynchronous mode. If you wish to run the PPP
protocols over your ISDN service, you need a specially modified version.
Details of where to find this version are available in the documentation
referred to above. Was_this_section_helpful?_Why_not_Donate_$2.50?
-------------------------------------------------------------------------------
11.2. PLIP for Linux-2.0
PLIP device names are `plip0', `plip1 and plip2.
Kernel Compile Options:
_____________________________________
|Network device support ---> |
| ____<*>_PLIP_(parallel_port)_support|
PLIP (Parallel Line IP) is similar to SLIP in that it is used for providing a
Point-to-Point network connection between two machines. However, it is designed
to use the parallel printer ports on your machine. It doesn't use the serial
ports (a cabling diagram in included in the cabling diagram section later in
this document). Because it is possible to transfer more than one bit at a time
with a parallel port, it is possible to attain higher speeds with the PLIP
interface. PLIP will attain higher speeds than those achieved by using a
standard serial device. In addition, even the simplest of parallel printer
ports can be used (in lieu of you having to purchase comparatively expensive
16550AFN UART's for your serial ports). PLIP uses a lot of CPU compared to a
serial link. It is not a good option if, for example, you are able to obtain
some cheap ethernet cards. However, it will work when nothing else is available
(and will work quite well). You should expect a data transfer rate of about 20
kilobytes per second (when a link is running well).
The PLIP device driver competes with the parallel device driver for the
parallel port hardware. If you wish to use both drivers, then you should
compile them both as modules. This ensures that you are able to select which
port you want to use for PLIP, and that you can select which ports you want for
the printer driver. Refer to the ``Modules mini-HOWTO'' for more information on
kernel module configuration.
Please note that some laptops use chipsets that will not work with PLIP. These
chipsets do not allow some combinations of signals. PLIP relies on these
signals, but printers don't use them.
The Linux PLIP interface is compatible with the Crynwyr Packet Driver PLIP/
.This will mean that you can connect your Linux machine to a DOS machine
running any other sort of tcp/ip software via PLIIP.
In the 2.0.* series kernel, the PLIP devices are mapped to i/o port and IRQ as
follows:
_________________
|device i/o IRQ |
| ------ ----- ---|
| plip0 0x3bc 5 |
| plip1 0x378 7 |
| plip2 0x278 2___|
If your parallel ports don't match any of the above combinations, then you can
change the IRQ of a port. Change the IRQ by using the ifconfig command with the
`irq' parameter (be sure to enable IRQ's on your printer ports in your ROM BIOS
if it supports this option). As an alternative, you can specify ``io='' and
``irq='' options on the insmod command line (if you use modules). For example:
__________________________________
|root#_insmod_plip.o_io=0x288_irq=5|
PLIP operation is controlled by two timeouts: their default values are probably
ok in most cases. You will more than likely need to increase them if you have
an especially slow computer. In this case the timers to increase are actually
on the other computer. A program called plipconfig exists that allows you to
change these timer settings without recompiling your kernel. This program is
supplied with many Linux distributions.
To configure a PLIP interface, you will need to invoke the following commands
(or add them to your initialization scripts):
___________________________________________________________
|root# /sbin/ifconfig plip1 localplip pointopoint remoteplip|
| root#_/sbin/route_add_remoteplip_plip1____________________|
Here, the port being used is the one at I/O address 0x378; localplip amd
remoteplip are the names or IP addresses used over the PLIP cable. I personally
keep them in my /etc/hosts database:
_________________________
|# plip entries |
| 192.168.3.1 localplip |
| 192.168.3.2___remoteplip|
The pointopoint parameter has the same meaning as for SLIP. It specifies the
address of the machine at the other end of the link.
In almost all respects, you can treat a PLIP interface as though it were a SLIP
interface. However, neither dip nor slattach can be used.
Further information on PLIP may be obtained from the ``PLIP mini-HOWTO''.
-------------------------------------------------------------------------------
11.2.1. PLIP for Linux-2.2
During development of the 2.1 kernel versions, support for the parallel port
was changed to an improved setup.
Kernel Compile Options:
_____________________________________
|General setup ---> |
| [*] Parallel port support |
| Network device support ---> |
| ____<*>_PLIP_(parallel_port)_support|
The new code for PLIP behaves like the old one. You can use the same ifconfig
and route commands as in the previous section. However, initialization of the
device is different due to the advanced parallel port support.
The ``first'' PLIP device is always called ``plip0'' (where first is the first
device detected by the system; similarly to what happens for Ethernet devices).
The actual parallel port being used is one of the available ports, as shown in
/proc/parport. For example, if you have only one parallel port, you'll only
have a directory called /proc/parport/0.
If your kernel didn't detect the IRQ number used by your port, ``insmod plip''
will fail. In this case just write the correct number to /proc/parport/0/
irq,then reinvoke insmod.
Complete information about parallel port management is available in the file
Documentation/parport.txt(part of your kernel sources).
-------------------------------------------------------------------------------
11.3. PPP
Due to the nature, size, complexity, and flexibility of PPP, it has been moved
to its own HOWTO. The PPP-HOWTO is still a Linux_Documentation_Project
document, but its official home is at the LinuxPorts.Com_website PPP_section.
Was_this_section_helpful?_Why_not_Donate_$2.50?
-------------------------------------------------------------------------------
11.4. SLIP client - (Antiquated)
SLIP devices are named `sl0', `sl1' etc. The first device configured is
assigned `0', and the rest of the devices are incremented sequentially as they
are configured.
Kernel Compile Options:
____________________________________
|Network device support ---> |
| [*] Network device support |
| <*> SLIP (serial line) support |
| [ ] CSLIP compressed headers |
| [ ] Keepalive and linefill |
| ____[_]__Six_bit_SLIP_encapsulation|
SLIP (Serial Line Internet Protocol) allows you to use tcp/ip over a serial
line (could be a phone line with a dialup modem, or a leased line of some
sort). To use SLIP, you would of course need access to an SLIP-server in your
area. Many universities and businesses provide SLIP access all over the world.
SLIP uses the serial ports on your machine to carry IP datagrams. To do this,
SLIP must take control of the serial device. SLIP device names are named sl0,
sl1 etc. How do these correspond to your serial devices? The networking code
uses what is called an ioctl (i/o control) call to change the serial devices
into SLIP devices. There are two programs supplied that can perform this
function: they are called dip and slattach
-------------------------------------------------------------------------------
11.4.1. dip
dip (Dialup IP) is a smart program that is able to perform the following tasks:
set the speed of the serial device, command your modem to dial the remote end
of the link, automatically log you into the remote server, search for messages
sent to you by the server, and extract information from them (such as your IP
address). It will then perform the ioctl necessary to switch your serial port
into SLIP mode. dip has a powerful scripting ability. It's this ability that
you can exploit to automate your logon procedure.
You can find it at: metalab.unc.edu.
Refer to the following for installation guidelines:
______________________________
|user% tar xvzf dip337o-uri.tgz|
| user% cd dip-3.3.7o |
| user% vi Makefile |
| root#_make_install___________|
The Makefile assumes the existence of a group called uucp. However, you might
like to change this to either dip or SLIP (depending on your configuration).
-------------------------------------------------------------------------------
11.4.2. slattach
slattach (as contrasted with dip) is a very simple program that does not have
the sophistication of dip. It does not have the scripting ability of dip. It
will only configure your serial device as a SLIP device. It assumes you have
all the information you need, and it figures that you have the serial line
established before you invoke it. slattach is ideal to use where you have a
permanent connection to your server (such as a physical cable or a leased
line).
-------------------------------------------------------------------------------
11.4.3. When do I use which ?
You would use dip when your link (to the machine that is your SLIP server) is
either a dialup modem or some other temporary link. You would use slattach when
you have a leased line, perhaps a cable, between your machine and the server:
it is assumed that there is no special action needed to get this link working.
See section `Permanen ist Slip connection' for more information.
Configuring SLIP is much like configuring an Ethernet interface (read section
`Configuring an ethernet device' above). There are a few key differences.
First of all, SLIP links are unlike ethernet networks in that there are only
two hosts on the network (one at each end of the link). Ethernet is available
for use as soon are you are cabled. However, SLIP may require you to initialize
your network connection in some special way (depending upon the type of link
that you have).
If you are using dip, then this would not normally be done at boot time. It
could be done at some later time, when you're ready to use the link. It is
possible to automate this procedure. If you are using slattach then you will
probably want to add a section to your rc.inet1 file. This will soon be
addressed in our document..
There are two major types of SLIP servers: Dynamic IP address servers and
static IP address servers. Almost every SLIP server will prompt you to login
using a username and password: dip can handle logging you in automatically.
-------------------------------------------------------------------------------
11.4.4. Static SLIP server with a dialup line and DIP.
A static SLIP server is one in which you have been supplied an IP address that
is exclusively yours. Each time you connect to the server, you will configure
your SLIP port with that address. The static SLIP server will answer your modem
call, possibly prompt you for a username and password, and then route any
datagrams destined for your address to you via that connection. If you have a
static server, then you may want to put entries for your hostname and IP
address (since you know what it will be) into your /etc/hosts. You should also
configure some other files such as: rc.inet2, host.conf, resolv.conf, /etc/
HOSTNAME and rc.local. Remember that when configuring rc.inet1, you don't need
to add any special commands for your SLIP connection (since it is dip that does
all of the hard work for you in configuring your interface). You will need to
give dip the appropriate information so it can configure the interface for you
(after it commands the modem to establish the call and it has logged you into
your SLIP server).
If this is how your SLIP server works, then you can move on to the section
`Using Dip' to learn how to configure dip it appropriately.
-------------------------------------------------------------------------------
11.4.5. Dynamic SLIP server with a dialup line and DIP.
A dynamic SLIP server is one which allocates you an IP address randomly (from a
pool of addresses) each time you logon. This means that there is no guarantee
that you will have any particular address. Address may well be used by someone
else after you have logged off. The network administrator who configured the
SLIP server will have assigned a pool of address for the SLIP server to use.
When the server receives a new incoming call, the following steps occur:
initially, it finds the first unused address; second, it guides the caller
through the login process; finally, it then prints a welcome message that
contains the IP address it has allocated. It will ultimately use that
particular IP address for the duration of the call.
Configuring for this type of server is similar to configuring for a static
server. You must add an extra step, however, where you obtain the IP address
the server has allocated to you. Then you can configure your SLIP device with
that address.
Again, dip does the hard work for you. New versions are smart enough to not
only log you in, but they are also able to automatically read the IP address
printed in the welcome message. They can then store this address so that you
can have your SLIP device configured.
If this is how your SLIP server works, then you can move to section `Using Dip'
to learn how to configure dip appropriately.
-------------------------------------------------------------------------------
11.4.6. Using DIP.
As explained earlier, dip is a powerful program that can simplify and automate
these process: dialing into the SLIP server, logging in the user, starting the
connection, and configuring the SLIP devices with the appropriate ifconfig and
route commands.
To use dip, you'll need to write a `dip script'. This script is basically a
list of commands that dip understands. These commands tell dip how to perform
each of the actions that you require. See sample.dip that comes supplied with
dip to get an idea of how it works. dip is quite a powerful program: it comes
with many options. Instead of going into all of them here, you should look at
the man page, README, and sample files that will have come with your version of
dip.
You may notice that the sample.dip script assumes that you're using a static
SLIP server (so you'll know what your IP address is beforehand). For dynamic
SLIP servers, the newer versions of dip include a command you can use to
automatically read and configure your SLIP device (with the IP address that the
dynamic server allocates for you). The following sample is a modified version
of the sample.dip that came supplied with dip337j-uri.tgz. It is probably a
good starting point for you. You might like to save it as /etc/dipscript, then
you can edit it to suit your configuration:
_______________________________________________________________________
| |
| # |
| # sample.dip Dialup IP connection support program. |
| # |
| # This file (should show) shows how to use the DIP |
| # This file should work for Annex type dynamic servers, if you |
| # use a static address server then use the sample.dip file that|
| # comes as part of the dip337-uri.tgz package. |
| # |
| # |
| # Version: @(#)sample.dip 1.40 07/20/93 |
| # |
| # Author: Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG> |
| # |
| main: |
| # Next, set up the other side's name and address. |
| # My dialin machine is called 'xs4all.hacktic.nl' (== 193.78.33.42) |
| get $remote xs4all.hacktic.nl |
| # Set netmask on sl0 to 255.255.255.0 |
| netmask 255.255.255.0 |
| # Set the desired serial port and speed. |
| port cua02 |
| speed 38400 |
| # Reset the modem and terminal line. |
| # This seems to cause trouble for some people! |
| reset |
| # Note! "Standard" pre-defined "errlevel" values: |
| # 0 - OK |
| # 1 - CONNECT |
| # 2 - ERROR |
| # |
| # You can change those grep'ping for "addchat()" in *.c... |
| # Prepare for dialing. |
| send ATQ0V1E1X4\r |
| wait OK 2 |
| if $errlvl != 0 goto modem_trouble |
| dial 555-1234567 |
| if $errlvl != 1 goto modem_trouble |
| # We are connected. Login to the system. |
| login: |
| sleep 2 |
| wait ogin: 20 |
| if $errlvl != 0 goto login_trouble |
| send MYLOGIN\n |
| wait ord: 20 |
| if $errlvl != 0 goto password_error |
| send MYPASSWD\n |
| loggedin: |
| # We are now logged in. |
| wait SOMEPROMPT 30 |
| if $errlvl != 0 goto prompt_error |
| # Command the server into SLIP mode |
| send SLIP\n |
| wait SLIP 30 |
| if $errlvl != 0 goto prompt_error |
| # Get and Set your IP address from the server. |
| # Here we assume that after commanding the SLIP server into SLIP |
| # mode that it prints your IP address |
| get $locip remote 30 |
| if $errlvl != 0 goto prompt_error |
| # Set up the SLIP operating parameters. |
| get $mtu 296 |
| # Ensure "route add -net default xs4all.hacktic.nl" will be done |
| default |
| # Say hello and fire up! |
| done: |
| print CONNECTED $locip ---> $rmtip |
| mode CSLIP |
| goto exit |
| prompt_error: |
| print TIME-OUT waiting for sliplogin to fire up... |
| goto error |
| login_trouble: |
| print Trouble waiting for the Login: prompt... |
| goto error |
| password:error: |
| print Trouble waiting for the Password: prompt... |
| goto error |
| modem_trouble: |
| print Trouble occurred with the modem... |
| error: |
| print CONNECT FAILED to $remote |
| quit |
| exit: |
| exit |
|_______________________________________________________________________|
The above example assumes you are calling a dynamic SLIP server. If you are
calling a static SLIP server, then the sample.dip file that comes with dip337j-
uri.tgz should work for you.
When dip is given the get $local command, it searches the incoming text from
the remote end for a string that looks like an IP address (ie strings numbers
separated by `.' characters). This modification was put in place specifically
for dynamic SLIP servers so that the process of reading the IP address granted
by the server could be automated.
The example above will automatically create a default route via your SLIP link.
If this is not what you want, you might have an ethernet connection that should
be your default route. Remove the default command from the script. After this
script has finished running (if you do an ifconfig command), you will see that
you have a device sl0. This is your SLIP device. You can modify its
configuration manually after the dip command has finished by using both the
ifconfig and the route commands.
Please note that dip allows you to select a number of different protocols to
use with the mode command. The most common example is cSLIP: it is used for
SLIP with compression. Please note that both ends of the link must agree. You
should ensure that whatever you select agrees with your server settings.
The above example is fairly robust, and it should cope with most errors. Please
refer to the dip man page for more information. Naturally, you could code the
script to do such things as redial the server if it doesn't get a connection
within a prescribed period of time. You can even try a series of servers (if
you have access to more than one).
-------------------------------------------------------------------------------
11.4.7. Permanent SLIP connection using a leased line and slattach.
If you have a cable between two machines (or are fortunate enough to have a
leased line), or some other permanent serial connection between your machine
and second machine, then you don't need to go to all the trouble of using dip
to set up your serial link. slattach is a very simple utility that will allow
you just enough functionality to configure your connection.
Since your connection will be a permanent one, you will want to add some
commands to your rc.inet1 file. To get a permanent connection, make sure that
you configure the serial device to the correct speed. Then switch the serial
device into SLIP mode. slattach allows you to do this with one command. Add the
following to your rc.inet1 file:
__________________________________________________________________
|# |
| # Attach a leased line static SLIP connection |
| # |
| # configure /dev/cua0 for 19.2kbps and cslip |
| /sbin/slattach -p cslip -s 19200 /dev/cua0 & |
| /sbin/ifconfig sl0 IPA.IPA.IPA.IPA pointopoint IPR.IPR.IPR.IPR up|
| # |
| #_End_static_SLIP._______________________________________________|
Where:
IPA.IPA.IPA.IPA
represents your IP address.
IPR.IPR.IPR.IPR
represents the IP address of the remote end.
slattach allocates the first unallocated SLIP device to the serial device
specified. slattach starts with sl0. The first slattach command attaches SLIP
device sl0 to the serial device specified; sl1 the next time, etc.
slattach allows you to configure a number of different protocols with the -
p argument. You will use either SLIP or cSLIP: the choice will depend on
whether or not you want to use compression. Note: both ends must agree on
compression or no compression.
-------------------------------------------------------------------------------
11.4.8. SLIP server.
If you have a machine that is perhaps network connected, and you'd like other
people be able to dial in and obtain network services, then you will need to
configure your machine as a server. If you want to use SLIP as the serial line
protocol, then you have three options as to how to configure your Linux machine
(as a SLIP server). My preference would be to use the first presented
(sliplogin) because it seems the easiest to configure and understand. I will
present a summary of each so that you can make your own decision.
-------------------------------------------------------------------------------
11.4.9. Slip Server using sliplogin.
sliplogin is a program that you can use in place of the normal login shell for
SLIP users. It converts the terminal line into a SLIP line. It also allows you
to configure your Linux machine as either a static address server (users get
the same address everytime they call in), or a dynamic address server (where
users may get a different address allocated to them each time they call).
The caller will login as per the standard login process by entering their
username and password. However, instead of being presented with a shell after
their login, sliplogin is executed. Sliplogin searches its configuration file
(/etc/slip.hosts) for an entry with a login name that matches that of the
caller. If it locates a match, it then configures the line as an 8bit clean
line. It uses an ioctl call to convert the line discipline to SLIP. When this
process is complete, the last stage of configuration takes place. Now sliplogin
invokes a shell script which configures the SLIP interface with the relevant ip
address and netmask. It will also set appropriate routing in place. This script
is usually called /etc/slip.login. In a similar manner to getty (where you have
certain callers that require special initialization) you can create
configuration scripts called /etc/slip.login.loginname. These scripts will be
run instead of the defaults.
There are either three or four files that you need to configure to get
sliplogin working for you. I will detail where to obtain the software and how
to configure in detail. The files are:
* /etc/passwd, for the dialin user accounts.
* /etc/slip.hosts, to contain the information unique to each dial-in user.
* /etc/slip.login, which manages the configuration of the routing that needs to
be performed for the user.
* /etc/slip.tty, which is required only if you are configuring your server for
dynamic address allocation. It contains a table of addresses to allocate.
* /etc/slip.logout, which contains commands to clean up after the user has hung
up or logged out.
-------------------------------------------------------------------------------
11.4.10. Where to get sliplogin
You may already have the sliplogin package installed as part of your
distribution. If you do not have the package, then you can get sliplogin from:
metalab.unc.edu. The tar file contains both source, precompiled binaries and a
man page.
To ensure that only authorized users will be able to run thesliplogin program,
you should add an entry to your /etc/group file similar to the following:
_____________________
| |
| .. |
| slip::13:radio,fred|
| .. |
|_____________________|
When you install the sliplogin package, the Makefile will change the group
ownership of the sliplogin program to slip. This will mean that only users who
belong to that group will be able to execute it. The example above will allow
only users radio and fred to execute sliplogin.
To install the binaries into your /sbin directory, and to place the man page
into section 8, perform the following:
_____________________________________________________________
| |
| # cd /usr/src |
| # gzip -dc .../sliplogin-2.1.1.tar.gz | tar xvf - |
| # cd sliplogin-2.1.1 |
| # <..edit the Makefile if you don't use shadow passwords..>|
| # make install |
|_____________________________________________________________|
If you want to recompile the binaries before installation, add a make clean
before the make install. If you want to install the binaries somewhere else,
you will need to edit the Makefile install rule.
-------------------------------------------------------------------------------
11.4.11. Configuring /etc/passwd for Slip hosts.
You would usually create some special logins for Slip callers in your /etc/
passwd file. A convention commonly followed is to use the hostname of the
calling host with a capital `S' prefixing it. If the calling host is called
radio then you could create a /etc/passwd entry that looked like:
_______________________________________________________________
| |
| Sradio:FvKurok73:1427:1:radio SLIP login:/tmp:/sbin/sliplogin|
|_______________________________________________________________|
It doesn't really matter what the account is called: just make it meaningful to
you!
Note: the caller doesn't need any special home directory. They will not be
presented with a shell from this machine, so /tmp is a good choice. Also note
that sliplogin is used in place of the normal login shell.
-------------------------------------------------------------------------------
11.4.12. Configuring /etc/slip.hosts
The /etc/slip.hosts file is the file that sliplogin searches (it looks for
entries matching the login name) to obtain configuration details for this
particular caller. It is this file where you specify the ip address and netmask
that will be assigned to the caller (configured for their use). Sample entries
for two hosts: one a static configuration for host radio, and another is a
dynamic configuration for user host albert.They both might look like:
____________________________________________________________________
| |
| # |
| Sradio 44.136.8.99 44.136.8.100 255.255.255.0 normal -1|
| Salbert 44.136.8.99 DYNAMIC 255.255.255.0 compressed 60|
| # |
|____________________________________________________________________|
The /etc/slip.hosts file entries are:
1. The login name of the caller.
2. The ip address of the server machine (ie: this machine).
3. This is the ip address that is assigned to the caller. If this field is
coded DYNAMIC, then an ip address will be allocated. This is based on the
information contained in your /etc/slip.tty file (to be discussed later).
Note: you must be using at least version 1.3 of sliplogin for this to
work.
4. The netmask assigned to the calling machine in dotted decimal notation eg
255.255.255.0 for a Class C network mask.
5. This is the slip mode setting which allows you to enable/disable
compression and slip other features. Allowable values here are either
"normal" or "compressed".
6. A timeout parameter which specifies how long the line can remain idle (no
datagrams received) before the line is automatically disconnected. A
negative value disables this feature.
7. Optional arguments.
Note: You can use either hostnames or IP addresses (in dotted decimal notation)
for fields 2 and 3. If you use hostnames, then those hosts must be resolvable.
In other words, your machine must be able to locate an IP address for those
hostnames. If the machine can't locate an IP address, the script will fail when
it is called. You can test this by trying to telnet to the hostname. If you get
the `Trying nnn.nnn.nnn...' message, then your machine has been able to find an
ip address for that name. If you get the message `Unknown host', then it was
unsuccessful. In this case, you can either use ip addresses in dotted decimal
notation, or fix up your name resolver configuration (See section Name
Resolution).
The most common slip modes are:
normal
to enable normal uncompressed SLIP.
compressed
to enable van Jacobsen header compression (cSLIP)
Naturally these are mutually exclusive. You can use one or the other. For more
information on the other options available, refer to the man pages.
-------------------------------------------------------------------------------
11.4.13. Configuring the /etc/slip.login file.
After sliplogin has searched the /etc/slip.hosts, and it has found a matching
entry, it will then attempt to execute the /etc/slip.login file. It will then
configure the SLIP interface with its ip address and netmask.
The sample /etc/slip.login file supplied with the sliplogin package looks like
this:
______________________________________________________________________
| |
| #!/bin/sh - |
| # |
| # @(#)slip.login 5.1 (Berkeley) 7/1/90 |
| # |
| # generic login file for a SLIP line. sliplogin invokes this with |
| # the parameters: |
| # $1 $2 $3 $4, $5, $6 ... |
| # SLIPunit ttyspeed pid the arguments from the slip.host entry|
| # |
| /sbin/ifconfig $1 $5 pointopoint $6 mtu 1500 -trailers up |
| /sbin/route add $6 |
| arp -s $6 <hw_addr> pub |
| exit 0 |
| # |
|______________________________________________________________________|
You will note that this script simply uses the ifconfig and route commands to
configure the SLIP device (with its IP address, remote IP address, and
netmask). The script then creates a route for the remote address via the SLIP
device. This procedure is the same as you would invoke if you were using the
slattach command.
Note also the use of Proxy ARP. It ensures that other hosts on the same
ethernet as the server machine will know how to reach the dial-in host. The
<hw_addr> field should be the hardware address of the ethernet card in the
machine. If your server machine isn't on an ethernet network, then you can
eliminate this line.
-------------------------------------------------------------------------------
11.4.14. Configuring the /etc/slip.logout file.
You want to ensure that the serial device is restored to its normal state when
the call drops out (so that future callers will be able to login correctly).
This is achieved with the use of the /etc/slip.logout file. It is quite simple
in format, and it is called with the same argument as the /etc/slip.login file.
____________________________
|#!/bin/sh - |
| # |
| # slip.logout|
| # |
| /sbin/ifconfig $1 down |
| arp -d $6 |
| exit 0 |
| #__________________________|
All it does is `down' the interface. This will delete the manual route
previously created. It also uses the arp command to delete any proxy arp put in
place. You don't need the arp command in the script if your server machine does
not have an ethernet port.
-------------------------------------------------------------------------------
11.4.15. Configuring the /etc/slip.tty file.
If you are using dynamic ip address allocation, you should have any hosts
configured with the DYNAMIC keyword in the /etc/slip.hosts file. You must then
configure the /etc/slip.tty file to list what addresses are assigned to what
port. You only need this file if you wish your server to dynamically allocate
addresses to users.
The file is a table that lists both the tty devices that will support dial-in
SLIP connections,and the ip address that should be assigned to users who call
in on that port.
Its format is as follows:
___________________________________________________________
| |
| # slip.tty tty -> IP address mappings for dynamic SLIP|
| # format: /dev/tty?? xxx.xxx.xxx.xxx |
| # |
| /dev/ttyS0 192.168.0.100 |
| /dev/ttyS1 192.168.0.101 |
| # |
|___________________________________________________________|
What this table says is that callers that dial in on port /dev/ttyS0 (who have
their remote address field in the /etc/slip.hosts file set to DYNAMIC) will be
assigned an address of 192.168.0.100.
In this way you need only allocate one address per port for all the users who
do not require dedicated address. This helps you keep the number of addresses
you need down to a minimum.
-------------------------------------------------------------------------------
11.4.16. Slip Server using dip.
Let me start by saying that some of the information below came from the dip man
pages (where how to run Linux as a SLIP server is briefly documented). Please
also beware that the following has been based on the dip337o-uri.tgz package,
and it probably will not apply to other versions of dip.
dip has an input mode of operation. In this mode, it automatically locates an
entry for the user who invoked it, and it then configures the serial line as a
SLIP link (according to information it finds in the /etc/diphosts file). This
input mode of operation is activated by invoking dip as diplogin. By creating
special accounts where diplogin is used as the login shell, you are using dip
as a SLIP server.
The first thing you will need to do is to make a symbolic link as follows:
___________________________________________
| |
| # ln -sf /usr/sbin/dip /usr/sbin/diplogin|
|___________________________________________|
You then need to add entries to both your /etc/passwd and your /etc/diphosts
files. The entries you need to make are formatted as follows:
To configure Linux as a SLIP server with dip, you need to create some special
SLIP accounts for users. You will use dip (in input mode) as the login shell. A
suggested convention is to have all SLIP accounts begin with a capital `S', eg
`Sfredm'.
A sample /etc/passwd entry for a SLIP user looks like the following:
_____________________________________________________________________
| |
| Sfredm:ij/SMxiTlGVCo:1004:10:Fred:/tmp:/usr/sbin/diplogin |
| ^^ ^^ ^^ ^^ ^^ ^^ ^^ |
| | | | | | | \__ diplogin as login shell|
| | | | | | \_______ Home directory |
| | | | | \____________ User Full Name |
| | | | \_________________ User Group ID |
| | | \_____________________ User ID |
| | \_______________________________ Encrypted User Password|
| \__________________________________________ Slip User Login Name |
|_____________________________________________________________________|
After the user logs in, the login program (if it finds and verifies the user)
will execute the diplogin command dip. diplogin knows that it should
automatically assume that it is being used a login shell. When it is started as
diplogin it uses the getuid() function call to get the userid from whoever has
invoked it. It then searches the /etc/diphosts file for the first entry that
matches either the userid or the name of the tty device from where the call has
originated. It then configures itself appropriately. By deciding between giving
the user an entry in the diphosts file, or providing her or him the default
configuration, you can build your server in such a way that you can have a mix
of static and dynamically assigned addressed users.
You do not need to worry about manually adding such entries because dip will
automatically add a `Proxy-ARP' entry if invoked in input mode.
-------------------------------------------------------------------------------
11.4.17. Configuring /etc/diphosts
/etc/diphosts is used by dip to lookup preset configurations for remote hosts.
These remote hosts might be users dialing into your linux machine, or they
might be for machines that you dial into with your linux machine.
The general format for /etc/diphosts is as follows:
______________________________________________________________________
| |
| .. |
| Suwalt::145.71.34.1:145.71.34.2:255.255.255.0:SLIP uwalt:CSLIP,1006 |
| ttyS1::145.71.34.3:145.71.34.2:255.255.255.0:Dynamic ttyS1:CSLIP,296|
| .. |
|______________________________________________________________________|
The fields are:
1. Login name: as returned by getpwuid(getuid()) or tty name.
2. Unused: compat. with passwd
3. Remote Address: IP address of the calling host, either numeric or by name
4. Local Address: IP address of this machine, again numeric or by name
5. Netmask: in dotted decimal notation
6. Comment field: place whatever you want here.
7. Protocol: Slip, CSlip etc.
8. MTU: decimal number
An example /etc/net/diphosts entry for a remote SLIP user might be:
___________________________________________________________________
| |
| Sfredm::145.71.34.1:145.71.34.2:255.255.255.0:SLIP uwalt:SLIP,296|
|___________________________________________________________________|
which specifies a SLIP link with remote address of 145.71.34.1 and MTU of 296,
or:
_____________________________________________________________________
| |
| Sfredm::145.71.34.1:145.71.34.2:255.255.255.0:SLIP uwalt:CSLIP,1006|
|_____________________________________________________________________|
which specifies a cSLIP-capable link with remote address 145.71.34.1 and MTU of
1006.
All users who you wish to be allowed a statically allocated dial-up IP access
should have an entry in the /etc/diphosts. If you want users who call a
particular port to have their details dynamically allocated, then you must have
an entry for the tty device (and do not configure a user based entry). You
should remember to configure at least one entry for each tty device that is
used. This ensures that a suitable configuration is available for them
regardless of which modem they call in on.
When a user logs in, they will receive a normal login and password prompt. They
should then enter their SLIP-login userid and password. If these verify
properly, then the user will see no special messages. The user should then
change into SLIP mode at their end. The user should then be able to connect and
be configured with the relevant parameters from the diphosts file.
-------------------------------------------------------------------------------
11.4.18. SLIP server using the dSLIP package.
Matt Dillon <dillon@apollo.west.oic.com> has written a package that does not
only dial-in but also dial-out SLIP. Matt's package is a combination of small
programs and scripts that manage your connections for you. You will need to
have tcsh installed as at least one of the scripts requires it. Matt supplies a
binary copy of the expect utility as it too is needed by one of the scripts.
You will most likely need some experience with expect to get this package
working to your liking, but don't let that deter your efforts!
Matt has written a good set of installation instructions in the README file, so
I won't bother to repeat them.
You can get the dSLIP package from its home site at:
apollo.west.oic.com
____________________________________
| |
| /pub/linux/dillon_src/dSLIP203.tgz|
|____________________________________|
or from:
metalab.unc.edu
_______________________________________________
| |
| /pub/Linux/system/Network/serial/dSLIP203.tgz|
|_______________________________________________|
Read the README file and create the /etc/passwd and /etc/group entries before
doing a make install.
-------------------------------------------------------------------------------
Chapter 12. Other Network Technologies
The following subsections are specific to particular network technologies. The
information contained in these sections does not necessarily apply to any other
type of network technology. The topics are sorted alphabetically.
-------------------------------------------------------------------------------
12.1. ARCNet
ARCNet device names are `arc0e', `arc1e', `arc2e' etc. or `arc0s', `arc1s',
`arc2s' etc. The first card detected by the kernel is assigned either `arc0e'
or `arc0s' The rest are assigned sequentially in the order they are detected.
The letter at the end signifies either the ethernet encapsulation packet format
or the RFC1051 packet format.
Kernel Compile Options:
____________________________________________________________
|Network device support ---> |
| [*] Network device support |
| <*> ARCnet support |
| [ ] Enable arc0e (ARCnet "Ether-Encap" packet format)|
| ____[_]___Enable_arc0s_(ARCnet_RFC1051_packet_format)______|
Once you have your kernel properly built to support your ethernet card, then
configuring the card is easy.
Typically you would use something like:
_____________________________________________________________
|root# ifconfig arc0e 192.168.0.1 netmask 255.255.255.0 up |
| root#_route_add_-net_192.168.0.0_netmask_255.255.255.0_arc0e|
Please refer to the /usr/src/linux/Documentation/networking/arcnet.txt and /
usr/src/linux/Documentation/networking/arcnet-hardware.txt files for further
information.
ARCNet support was developed by Avery Pennarun, apenwarr@foxnet.net. Was_this
section_helpful?_Why_not_Donate_$2.50?
-------------------------------------------------------------------------------
12.2. Appletalk (AF_APPLETALK)
The Appletalk support has no special device names as it uses existing network
devices.
Kernel Compile Options:
________________________
|Networking options --->|
| ____<*>_Appletalk_DDP__|
Appletalk support allows your Linux machine to interwork with Apple networks.
An important use for this is to share resources (such as printers and disks)
between your Linux and Apple computers. Additional software is required; this
is called netatalk. Wesley Craig netatalk@umich.edu represents a team called
the `Research Systems Unix Group' at the University of Michigan. They have
produced the netatalk package. This product provides software that implements
the Appletalk protocol stack along with some useful utilities. The netatalk
package will either be supplied with your Linux distribution, or you will have
to ftp it from the home site at University_of_Michigan
To build and install the package, do something like the following:
_______________________________________
|user% tar xvfz .../netatalk-1.4b2.tar.Z|
| user% make |
| root#_make_install____________________|
You may want to edit the `Makefile' before calling make to actually compile the
software. Specifically, you might want to change the DESTDIR variable that
defines where the files will later be installed. The default of /usr/local/
atalk is fairly safe.
-------------------------------------------------------------------------------
12.2.1. Configuring the Appletalk software.
The first thing you need to do to make it all work is to ensure that the
appropriate entries in the /etc/services file are present. The entries you need
are:
___________________________________________________
| |
| rtmp 1/ddp # Routing Table Maintenance Protocol|
| nbp 2/ddp # Name Binding Protocol |
| echo 4/ddp # AppleTalk Echo Protocol |
| zip 6/ddp # Zone Information Protocol |
|___________________________________________________|
The next step is to create the Appletalk configuration files in the /usr/local/
atalk/etc directory (or wherever you installed the package).
The first file to create is the /usr/local/atalk/etc/atalkd.conf file. This
file initially needs only one line. This line gives the name of the network
device supporting the network that your Apple machines are on:
________
| |
| eth0|
|________|
The Appletalk daemon program will add extra details after it has been
initiated.
-------------------------------------------------------------------------------
12.2.2. Exporting a Linux filesystems via Appletalk.
You can export filesystems from your linux machine to the network so that any
Apple machine on the network can share them.
To do this you must configure the /usr/local/atalk/etc/AppleVolumes.system
file. There is another configuration file called /usr/local/atalk/etc/
AppleVolumes.default This file has exactly the same format: it describes which
filesystems users connecting with guest privileges will receive.
Full details on how to configure these files (and their various options) can be
found in the afpd man page.
A simple example might look like:
_______________________________
| |
| /tmp Scratch |
| /home/ftp/pub "Public Area"|
|_______________________________|
This would export your /tmp filesystem as AppleShare Volume `Scratch', and it
would export your ftp public directory as AppleShare Volume `Public Area'. The
volume names are not mandatory. The daemon will choose some for you, but it
won't hurt to specify them anyway.
-------------------------------------------------------------------------------
12.2.3. Sharing your Linux printer across Appletalk.
It is simple to share your linux printer with your Apple machines. You need to
run the papd program, the Appletalk Printer Access Protocol Daemon. When you
run this program, it will accept requests from your Apple machines and spool
the print job to your local line printer daemon.
You need to edit the /usr/local/atalk/etc/papd.conf file to configure the
daemon. The syntax of this file is the same as that of your usual /etc/printcap
file. The name you give to the definition is registered with the Appletalk
naming protocol NBP.
A sample configuration might look like:
____________________
| |
| TricWriter:\ |
| :pr=lp:op=cg:|
|____________________|
This would make a printer named `TricWriter' available to your Appletalk
network. All accepted jobs would be printed to the linux printer `lp' (as
defined in the /etc/printcap file) using lpd. The entry `op=cg' says that the
linux user `cg' is the operator of the printer.
-------------------------------------------------------------------------------
12.2.4. Starting the appletalk software.
Ok.You should now be ready to test this basic configuration. There is an
rc.atalk file supplied with the netatalk package that should work ok for you,
so all you should have to do is:
___________________________________
|root#_/usr/local/atalk/etc/rc.atalk|
All should startup and run ok. You should see no error messages. The software
will send messages to the console indicating each stage as it starts.
-------------------------------------------------------------------------------
12.2.5. Testing the appletalk software.
To test that the software is functioning properly: go to one of your Apple
machines, pull down the Apple menu, select the Chooser, click on AppleShare,
and your Linux box should appear.
-------------------------------------------------------------------------------
12.2.6. Caveats of the appletalk software.
* You may need to start the Appletalk support before you configure your IP
network. If you have problems starting the Appletalk programs (or if after
you start them you have trouble with your IP network), then try starting the
Appletalk software before you run your /etc/rc.d/rc.inet1 file.
* The afpd (Apple Filing Protocol Daemon) SEVERELY MESSES UP YOUR HARD DISK. It
creates a couple of directories called ``.AppleDesktop'' and Network Trash
Folder below the mount points. For each directory you access, it will create
a .AppleDouble below it so it can store resource forks, etc. Think twice
before exporting /; you will have a great time cleaning up afterwards.
* The afpd program expects clear text passwords from the Macs. Security could
be a problem, so be very careful when you run this daemon on a machine
connected to the Internet. You only have yourself to blame if somebody nasty
does something bad!
* The existing diagnostic tools (such as netstat and ifconfig) don't support
Appletalk. The raw information is available in the /proc/net/ directory.
-------------------------------------------------------------------------------
12.2.7. More information
For a much more detailed description of how to configure Appletalk for Linux,
refer to Anders Brownworth Linux Netatalk-HOWTO page at thehamptons.com.
-------------------------------------------------------------------------------
12.3. ATM
Werner Almesberger <werner.almesberger@lrc.di.epfl.ch> is managing a project to
provide Asynchronous Transfer Mode support for Linux. Current information on
the status of the project may be obtained from: lrcwww.epfl.ch. Was_this
section_helpful?_Why_not_Donate_$2.50?
-------------------------------------------------------------------------------
12.4. AX25 (AF_AX25)
AX.25 device names are `sl0', `sl1', etc. in 2.0.* kernels or `ax0', `ax1',
etc. in 2.1.* kernels.
Kernel Compile Options:
____________________________________
|Networking options ---> |
| ____[*]_Amateur_Radio_AX.25_Level_2|
The AX25, Netrom and Rose protocols are covered by the AX25-HOWTO. These
protocols are used by Amateur Radio Operators world wide in packet radio
experimentation.
Most of the work for implementation of these protocols has been done by
Jonathon Naylor: jsn@cs.nott.ac.uk. Was_this_section_helpful?_Why_not_Donate
$2.50?
-------------------------------------------------------------------------------
12.5. DECNet
Support for DECNet is currently a work in progress. You should expect it to
appear in a late 2.1.* kernel. Was_this_section_helpful?_Why_not_Donate_$2.50?
-------------------------------------------------------------------------------
12.6. FDDI
FDDI device names are `fddi0', `fddi1', `fddi2' etc. The first card detected by
the kernel is assigned `fddi0' : the rest are assigned sequentially in the
order that they are detected.
Larry Stefani, lstefani@ultranet.com, has developed a driver for the Digital
Equipment Corporation FDDI EISA and PCI cards.
Kernel Compile Options:
________________________________________________
|Network device support ---> |
| [*] FDDI driver support |
| ____[*]_Digital_DEFEA_and_DEFPA_adapter_support|
When you have your kernel built and installed to support the FDDI driver,
configuration of the FDDI interface is almost identical to that of an ethernet
interface. You just specify the appropriate FDDI interface name in the ifconfig
and route commands. Was_this_section_helpful?_Why_not_Donate_$2.50?
-------------------------------------------------------------------------------
12.7. Frame Relay
The Frame Relay device names are `dlci00', `dlci01' etc for the DLCI
encapsulation devices, and `sdla0', `sdla1' etc for the FRAD(s).
Frame Relay is a new networking technology that is designed to suit data
communications traffic that is of a `bursty' or intermittent nature. You
connect to a Frame Relay network using a Frame Relay Access Device (FRAD). The
Linux Frame Relay supports IP over Frame Relay as described in RFC-1490.
Kernel Compile Options:
________________________________________________
|Network device support ---> |
| <*> Frame relay DLCI support (EXPERIMENTAL)|
| (24) Max open DLCI |
| (8) Max DLCI per device |
| ____<*>___SDLA_(Sangoma_S502/S508)_support_____|
Mike McLagan, mike.mclagan@linux.org, developed the Frame Relay support and
configuration tools.
Currently the only FRAD I know of that are supported are Sangoma_Technologies
S502A, S502E , S508, and the Emerging Technologies. The Emerging Technologies
website is found at: here.
I would like to make a point at this juncture. I have personal experience with
Emerging Technologies, and I do not recommend them. I found thier staff to be
very unprofessional and extremely rude. If anyone else has been fortunate
enough to have a good experience with them, I would like to know. I will say
this for Emerging Technologies: their product is flexible, and it and appears
to be stable.
To configure the FRAD and DLCI devices (after you have rebuilt your kernel),
you will need the Frame Relay configuration tools. These are available from
ftp.invlogic.com.
Compiling and installing the tools is straightforward, but the lack of a top
level Makefile makes it a fairly manual process:
____________________________________________________________________
|user% tar xvfz .../frad-0.15.tgz |
| user% cd frad-0.15 |
| user% for i in common dlci frad; make -C $i clean; make -C $i; done|
| root# mkdir /etc/frad |
| root# install -m 644 -o root -g root bin/*.sfm /etc/frad |
| root# install -m 700 -o root -g root frad/fradcfg /sbin |
| rppt#_install_-m_700_-o_root_-g_root_dlci/dlcicfg_/sbin____________|
Note that the previous commands use sh syntax. If you use a csh flavour instead
(like tcsh), the for loop will look different.
After installing the tools, you need to create an /etc/frad/router.conf file.
You can use this template (which is a modified version of one of the example
files):
___________________________________________________________________________
| |
| # /etc/frad/router.conf |
| # This is a template configuration for frame relay. |
| # All tags are included. The default values are based on the code |
| # supplied with the DOS drivers for the Sangoma S502A card. |
| # |
| # A '#' anywhere in a line constitutes a comment. |
| # Blanks are ignored (you can indent with tabs too). |
| # Unknown [] entries and unknown keys are ignored . |
| # |
| [Devices] |
| Count=1 # number of devices to configure |
| Dev_1=sdla0 # the name of a device |
| #Dev_2=sdla1 # the name of a device |
| # Specified here, these are applied to all devices and can be overridden |
| for |
| # each individual board. |
| # |
| Access=CPE |
| Clock=Internal |
| KBaud=64 |
| Flags=TX |
| # |
| # MTU=1500 # Maximum transmit IFrame length, default is 4096|
| # T391=10 # T391 value 5 - 30, default is 10 |
| # T392=15 # T392 value 5 - 30, default is 15 |
| # N391=6 # N391 value 1 - 255, default is 6 |
| # N392=3 # N392 value 1 - 10, default is 3 |
| # N393=4 # N393 value 1 - 10, default is 4 |
| # Specified here, these set the defaults for all boards |
| # CIRfwd=16 # CIR forward 1 - 64 |
| # Bc_fwd=16 # Bc forward 1 - 512 |
| # Be_fwd=0 # Be forward 0 - 511 |
| # CIRbak=16 # CIR backward 1 - 64 |
| # Bc_bak=16 # Bc backward 1 - 512 |
| # Be_bak=0 # Be backward 0 - 511 |
| # |
| # |
| # Device specific configuration |
| # |
| # |
| # |
| # The first device is a Sangoma S502E |
| # |
| [sdla0] |
| Type=Sangoma # Type of the device to configure, currently only|
| # SANGOMA is recognized |
| # |
| # These keys are specific to the 'Sangoma' type |
| # |
| # The type of Sangoma board - S502A, S502E, S508 |
| Board=S502E |
| # |
| # The name of the test firmware for the Sangoma board |
| # Testware=/usr/src/frad-0.10/bin/sdla_tst.502 |
| # |
| # The name of the FR firmware |
| # Firmware=/usr/src/frad-0.10/bin/frm_rel.502 |
| # |
| Port=360 # Port for this particular card |
| Mem=C8 # Address of memory window, A0-EE, depending on |
| card |
| IRQ=5 # IRQ number, do not supply for S502A |
| DLCIs=1 # Number of DLCI's attached to this device |
| DLCI_1=16 # DLCI #1's number, 16 - 991 |
| # DLCI_2=17 |
| # DLCI_3=18 |
| # DLCI_4=19 |
| # DLCI_5=20 |
| # |
| # Specified here, these apply to this device only, |
| # and override defaults from above |
| # |
| # Access=CPE # CPE or NODE, default is CPE |
| # Flags=TXIgnore,RXIgnore,BufferFrames,DropAborted,Stats,MCI,AutoDLCI |
| # Clock=Internal # External or Internal, default is Internal |
| # Baud=128 # Specified baud rate of attached CSU/DSU |
| # MTU=2048 # Maximum transmit IFrame length, default is 4096|
| # T391=10 # T391 value 5 - 30, default is 10 |
| # T392=15 # T392 value 5 - 30, default is 15 |
| # N391=6 # N391 value 1 - 255, default is 6 |
| # N392=3 # N392 value 1 - 10, default is 3 |
| # N393=4 # N393 value 1 - 10, default is 4 |
| # |
| # The second device is some other card |
| # |
| # [sdla1] |
| # Type=FancyCard # Type of the device to configure. |
| # Board= # Type of Sangoma board |
| # Key=Value # values specific to this type of device |
| # |
| # DLCI Default configuration parameters |
| # These may be overridden in the DLCI specific configurations |
| # |
| CIRfwd=64 # CIR forward 1 - 64 |
| # Bc_fwd=16 # Bc forward 1 - 512 |
| # Be_fwd=0 # Be forward 0 - 511 |
| # CIRbak=16 # CIR backward 1 - 64 |
| # Bc_bak=16 # Bc backward 1 - 512 |
| # Be_bak=0 # Be backward 0 - 511 |
| # |
| # DLCI Configuration |
| # These are all optional. The naming convention is |
| # [DLCI_D<devicenum>_<DLCI_Num>] |
| # |
| [DLCI_D1_16] |
| # IP= |
| # Net= |
| # Mask= |
| # Flags defined by Sangoma: TXIgnore,RXIgnore,BufferFrames |
| # DLCIFlags=TXIgnore,RXIgnore,BufferFrames |
| # CIRfwd=64 |
| # Bc_fwd=512 |
| # Be_fwd=0 |
| # CIRbak=64 |
| # Bc_bak=512 |
| # Be_bak=0 |
| [DLCI_D2_16] |
| # IP= |
| # Net= |
| # Mask= |
| # Flags defined by Sangoma: TXIgnore,RXIgnore,BufferFrames |
| # DLCIFlags=TXIgnore,RXIgnore,BufferFrames |
| # CIRfwd=16 |
| # Bc_fwd=16 |
| # Be_fwd=0 |
| # CIRbak=16 |
| # Bc_bak=16 |
| # Be_bak=0 |
|___________________________________________________________________________|
After you've built your /etc/frad/router.conf file, the only step remaining is
to configure the actual devices. This is only a little trickier than a normal
network device configuration. Remember to bring up the FRAD device before the
DLCI encapsulation devices. These commands are best hosted in a shell script
because of their number:
__________________________________________________________
|#!/bin/sh |
| # Configure the frad hardware and the DLCI parameters |
| /sbin/fradcfg /etc/frad/router.conf || exit 1 |
| /sbin/dlcicfg file /etc/frad/router.conf |
| # |
| # Bring up the FRAD device |
| ifconfig sdla0 up |
| # |
| # Configure the DLCI encapsulation interfaces and routing|
| ifconfig dlci00 192.168.10.1 pointopoint 192.168.10.2 up |
| route add -net 192.168.10.0 netmask 255.255.255.0 dlci00 |
| # |
| ifconfig dlci01 192.168.11.1 pointopoint 192.168.11.2 up |
| route add -net 192.168.11.0 netmask 255.255.255.0 dlci00 |
| # |
| route add default dev dlci00 |
| #________________________________________________________|
Was_this_section_helpful?_Why_not_Donate_$2.50?
-------------------------------------------------------------------------------
12.8. IPX (AF_IPX)
The IPX protocol is most commonly utilized in Novell NetWare(tm) local area
network environments. Linux includes support for this protocol, and it may be
configured to act as a network endpoint (or, as a router for IPX).
Kernel Compile Options:
__________________________________
|Networking options ---> |
| [*] The IPX protocol |
| ____[_]_Full_internal_IPX_network|
The IPX protocol and the NCPFS are covered in greater depth in the IPX-HOWTO.
Was_this_section_helpful?_Why_not_Donate_$2.50?
-------------------------------------------------------------------------------
12.9. NetRom (AF_NETROM)
NetRom device names are `nr0', `nr1', etc.
Kernel Compile Options:
____________________________________
|Networking options ---> |
| [*] Amateur Radio AX.25 Level 2|
| ____[*]_Amateur_Radio_NET/ROM______|
The AX25, Netrom and Rose protocols are covered by the AX25-HOWTO. These
protocols are used by Amateur Radio Operators world wide in packet radio
experimentation.
Most of the work for implementation of these protocols has been done by
Jonathon Naylor, jsn@cs.nott.ac.uk. Was_this_section_helpful?_Why_not_Donate
$2.50?
-------------------------------------------------------------------------------
12.10. Rose protocol (AF_ROSE)
Rose device names are `rs0', `rs1', etc. in 2.1.* kernels. Rose is available in
the 2.1.* kernels.
Kernel Compile Options:
______________________________________
|Networking options ---> |
| [*] Amateur Radio AX.25 Level 2 |
| ____<*>_Amateur_Radio_X.25_PLP_(Rose)|
The AX25, Netrom and Rose protocols are covered by the AX25-HOWTO. These
protocols are used by Amateur Radio Operators world wide in packet radio
experimentation.
Most of the work for implementation of these protocols has been done by
Jonathon Naylor: jsn@cs.nott.ac.uk. Was_this_section_helpful?_Why_not_Donate
$2.50?
-------------------------------------------------------------------------------
12.11. SAMBA - `NetBEUI', `NetBios', `CIFS' support.
SAMBA is an implementation of the Session Management Block protocol. Samba
allows Microsoft and other systems to mount and use your disks and printers.
SAMBA and its configuration are covered in detail in the SMB-HOWTO. Was_this
section_helpful?_Why_not_Donate_$2.50?
-------------------------------------------------------------------------------
12.12. STRIP support (Starmode Radio IP)
STRIP device names are `st0', `st1', etc.
Kernel Compile Options:
________________________________________
|Network device support ---> |
| [*] Network device support |
| .... |
| [*] Radio network interfaces |
| <_>_STRIP_(Metricom_starmode_radio_IP)|
STRIP is a protocol designed (specifically for a range of Metricom radio
modems) for a research project being conducted by Stanford University called
the MosquitoNet_Project. There is a lot of interesting reading here (even if
you aren't directly interested in the project).
The Metricom radios connect to a serial port, employ spread spectrum technology
and are typically capable of about 100kbps. Information on the Metricom radios
is available from: Metricom_Web_Server.
The standard network tools and utilities currently do not support the STRIP
driver. You will have to download some customized tools from the MosquitoNet
web server. Details on what software you need is available at: MosquitoNet
STRIP_Page.
A summary of the configuration is that you use a modified slattach program to
set the line discipline of a serial tty device to STRIP. Configure the
resulting `st[0-9]' device as you would for ethernet with one important
exception: for technical reasons, STRIP does not support the ARP protocol, so
you must manually configure the ARP entries for each of the hosts on your
subnet. This shouldn't prove too onerous! Was_this_section_helpful?_Why_not
Donate_$2.50?
-------------------------------------------------------------------------------
12.13. Token Ring
Token ring device names are `tr0', `tr1' etc. Token Ring is an IBM standard LAN
protocol that avoids collisions by providing a mechanism that allows only one
station on the LAN the right to transmit at a time. A `token' is held by one
station. This station is the only one allowed to transmit. When it has
transmitted its data, it then passes the token onto the next station. The token
loops amongst all active stations; hence the name `Token Ring'.
Kernel Compile Options:
______________________________________________
|Network device support ---> |
| [*] Network device support |
| .... |
| [*] Token Ring driver support |
| <_>_IBM_Tropic_chipset_based_adaptor_support|
Configuration of token ring is identical to that of ethernet except for
configuring the network device name. Was_this_section_helpful?_Why_not_Donate
$2.50?
-------------------------------------------------------------------------------
12.14. X.25
X.25 is a circuit based packet switching protocol defined by the C.C.I.T.T. (a
standards body recognized by Telecommunications companies in most parts of the
world). Implementations of X.25 and LAPB are currently being worked on, and
recent 2.1.* kernels include the work in progress.
Jonathon Naylor jsn@cs.nott.ac.uk is leading the development. A mailing list
has been established to discuss Linux X.25 related matters. If you'd like to
subscribe, send a message to: majordomo@vger.rutgers.edu. Be sure to include
the text "subscribe linux-x25" in the body of the message.
Early versions of the configuration tools may be obtained from Jonathon's ftp
site at :ftp.cs.nott.ac.uk.
Was_this_section_helpful?_Why_not_Donate_$2.50?
-------------------------------------------------------------------------------
12.15. WaveLan Card
Wavelan device names are `eth0', `eth1', etc.
Kernel Compile Options:
_______________________________
| |
| Network device support ---> |
| [*] Network device support |
| .... |
| [*] Radio network interfaces|
| .... |
| <*> WaveLAN support |
|_______________________________|
The WaveLAN card is a spread spectrum wireless lan card. The card looks very
much like an ethernet card, and it is configured in much the same manner.
You can get information on the Wavelan card from Wavelan.com. Was_this_section
helpful?_Why_not_Donate_$2.50?
-------------------------------------------------------------------------------
Chapter 13. Cables and Cabling
Those of you handy with a soldering iron may want to build your own cables to
interconnect two linux machines. The following cabling diagrams should assist
you with your little project.
-------------------------------------------------------------------------------
13.1. Serial NULL Modem cable
Not all NULL modem cables are alike. Many null modem cables do little more than
trick your computer into thinking all the appropriate signals are present (and
then swap transmit and receive data). This is ok, but it means that you must
use software flow control (XON/XOFF) that is less efficient than hardware flow
control. The following cable provides the best possible signalling between
machines, and it allows you to use hardware (RTS/CTS) flow control.
_________________________________________________
| |
| Pin Name Pin Pin|
| Tx Data 2 ----------------------------- 3 |
| Rx Data 3 ----------------------------- 2 |
| RTS 4 ----------------------------- 5 |
| CTS 5 ----------------------------- 4 |
| Ground 7 ----------------------------- 7 |
| DTR 20 -\--------------------------- 8 |
| DSR 6 -/ |
| RLSD/DCD 8 ---------------------------/- 20|
| \- 6 |
|_________________________________________________|
Was_this_section_helpful?_Why_not_Donate_$2.50?
-------------------------------------------------------------------------------
13.2. Parallel port cable (PLIP cable)
If you intend to use the PLIP protocol between two machines, then this cable
will work for you (irrespective of what sort of parallel ports you have
installed).
________________________________
| |
| Pin Name pin pin|
| STROBE 1* |
| D0->ERROR 2 ----------- 15 |
| D1->SLCT 3 ----------- 13 |
| D2->PAPOUT 4 ----------- 12 |
| D3->ACK 5 ----------- 10 |
| D4->BUSY 6 ----------- 11 |
| D5 7* |
| D6 8* |
| D7 9* |
| ACK->D3 10 ----------- 5 |
| BUSY->D4 11 ----------- 6 |
| PAPOUT->D2 12 ----------- 4 |
| SLCT->D1 13 ----------- 3 |
| FEED 14* |
| ERROR->D0 15 ----------- 2 |
| INIT 16* |
| SLCTIN 17* |
| GROUND 25 ----------- 25 |
|________________________________|
Notes:
* Do not connect the pins marked with an asterisk `*'.
* Extra grounds are 18,19,20,21,22,23 and 24.
* If the cable you are using has a metallic shield, it should be connected to
the metallic DB-25 shell at one end only.
Warning: A miswired PLIP cable can destroy your controller card. Be very
careful! Be sure to double check every connection to ensure that you don't
cause yourself any unnecessary work or heartache.
While you may be able to run PLIP cables for long distances, you should avoid
it if you can. The specifications for the cable allow for a cable length of
about 1 meter or so. Please be very careful when running long PLIP cables as
sources of strong electromagnetic fields (such as lightning, power lines, and
radio transmitters) can interfere with and sometimes even damage your
controller. If you really want to connect two of your computers over a large
distance, then you really should be looking at obtaining a pair of thin-net
ethernet cards (and running some coaxial cable). Was_this_section_helpful?_Why
not_Donate_$2.50?
-------------------------------------------------------------------------------
13.3. 10base2 (thin coax) Ethernet Cabling
10base2 is an ethernet cabling standard that specifies the use of 50 ohm
coaxial cable that has a diameter of about 5 millimeters. There are a couple of
important rules to remember when interconnecting machines with 10base2 cabling.
The first is that you must use terminators at both ends of the cabling. A
terminator is a 50 ohm resistor that helps to ensure that the signal is
absorbed (and not reflected) when it reaches the end of the cable. Without a
terminator at each end of the cabling, you may find that the ethernet is
unreliable (or doesn't work). Normally you'd use `T pieces' to interconnect the
machines. You would end up with something that looks like this:
_________________________________________________________________
| |
| |==========T=============T=============T==========T==========||
| | | | | |
| | | | | |
| ----- ----- ----- ----- |
| | | | | | | | | |
| ----- ----- ----- ----- |
|_________________________________________________________________|
The `|' at either end represents a terminator, the `======' represents a length
of coaxial cable with BNC plugs at either end, and the `T' represents a `T
piece' connector. You should keep the length of cable between the `T piece' and
the actual ethernet card in the PC as short as possible. The `T piece' will
ideally be plugged directly into the ethernet card. Was_this_section_helpful?
Why_not_Donate_$2.50?
-------------------------------------------------------------------------------
13.4. Twisted Pair Ethernet Cable
If you have only two twisted pair ethernet cards (and you wish to connect
them), you do not require a hub. You can cable the two cards directly together.
A diagram showing how to do this is included in the Ethernet-HOWTO Was_this
section_helpful?_Why_not_Donate_$2.50?
-------------------------------------------------------------------------------
Chapter 14. Glossary of Terms used in this document.
The following is a list of some of the most important terms used in this
document.
ARP
This is an acronym for the Address Resolution Protocol . It is how a
network machine associates an IP Address with a hardware address.
ATM
This is an acronym for Asynchronous Transfer Mode. An ATM network
packages data into standard size blocks which it can convey efficiently
from point to point. ATM is a circuit switched packet network technology.
Client
This is usually the piece of software at the end of a system where the
user is located. There are exceptions. For example, in the X11 window
system, it is actually the server with the user and the client runs on
the remote machine. The client is the program (or end) of a system that
is receiving the service provided by the server. In the case of peer to
peer systems such as slip or ppp, the client is taken to be the end that
initiates the connection. The remote end being called is taken to be the
server.
Datagram
A datagram is a discrete package of data and headers which contain
addresses (which is the basic unit of transmission across an IP network).
You might also hear this called a `packet'.
DLCI
The DLCI is the Data Link Connection Identifier. It is used to identify a
unique virtual Point-to-Point connection via a Frame Relay network. The
DLCI's are normally assigned by the Frame Relay network provider.
Frame Relay
Frame Relay is a network technology ideally suited to carrying traffic
that is of bursty or sporadic in nature. Network costs are reduced by
having many Frame Relay customer sharing the same network capacity (and
relying on them wanting to make use of the network at slightly different
times).
Hardware address
This is a number that uniquely identifies a host in a physical network at
the media access layer. Examples of this are Ethernet Addresses and AX.25
Addresses.
ISDN
This is an acronym for Integrated Services Digital Network. ISDN provides
a standardized means by which Telecommunications companies may deliver
either voice or data information to a customers premises. ISDN is
technically a circuit switched data network.
ISP
This is an acronym for an Internet Service Provider. These are
organizations or companies that provide people with network connectivity
to the Internet.
IP address
This is a number that uniquely identifies a TCP/IP host on the network.
The address is 4 bytes long and is usually represented in what is called
the "dotted decimal notation" (where each byte is represented in decimal
from with dots `.' between them).
MSS
The Maximum Segment Size (MSS) is the largest quantity of data that can
be transmitted at one time. If you want to prevent local fragmentation,
MSS would equal MTU-IP header.
MTU
The Maximum Transmission Unit (MTU) is a parameter that determines the
largest datagram than can be transmitted by an IP interface (without it
needing to be broken down into smaller units). The MTU should be larger
than the largest datagram you wish to transmit unfragmented. Note: this
only prevents fragmentation locally. Some other link in the path may have
a smaller MTU: the datagram will be fragmented at that point. Typical
values are 1500 bytes for an ethernet interface, or 576 bytes for a SLIP
interface.
Route
The route is the path that your datagrams take through the network to
reach their destination.
Server
This is usually the piece of software or end of a system remote from the
user. The server provides some service to one or many clients. Examples
of servers include ftp, Networked File System, or Domain Name Server. In
the case of peer to peer systems (such as slip or ppp ), the server is
taken to be the end of the link that is called. The end calling is taken
to be the client.
Window
The window is the largest amount of data that the receiving end can
accept at a given point in time.
-------------------------------------------------------------------------------
Chapter 15. Authors
15.1. Current
Joshua D. Drake
Was_this_section_helpful?_Why_not_Donate_$2.50?
-------------------------------------------------------------------------------
15.2. Past
Terry Dawson Alessandro Rubini Was_this_section_helpful?_Why_not_Donate_$2.50?
-------------------------------------------------------------------------------
Chapter 16. Copyright.
Copyright Information
The NET-3/4-HOWTO,NET-3, and Networking-HOWTO, information on how to install
and configure networking support for Linux. Copyright (c) 1997 Terry Dawson,
1998 Alessandro Rubini, 1999 & 2000 Joshua D. Drake {POET}/CommandPrompt, Inc.
- http://www.linuxports.com/
This program is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free Software
Foundation; either version 2 of the License, or (at your option) any later
version. This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
details. You should have received a copy of the GNU General Public License
along with this program; if not, write to the: Free Software Foundation, Inc.,
675 Mass Ave, Cambridge, MA 02139, USA.