Following are examples of the most common types of configurations. These
are guides only as there are as many ways of configuring your network as there
are networks to configure, but they may give you a start.
Many of you may have small local area networks at home and want to
connect the machines on that network to your local radio LAN. This is
the type of configuration I use at home. I arranged to have a suitable
block of addresses allocated to me that I could capture in a single route
for convenience and I use these on my Ethernet LAN. Your local IP coordinator
will assist you in doing this if you want to try it as well. The addresses
for the Ethernet LAN form a subset of the radio LAN addresses. The following
configuration is the actual one for my linux router on my network at home:
Some information here on tunnelling is out of date. The setup has
changed since the 2.0.x kernel, now the "ip" command from the iproute2
package should be used, as described in the Advanced Routing
Linux is now very commonly used for TCP/IP encapsulated gateways around
the world. The new tunnel driver supports multiple encapsulated routes
and makes the older ipip daemon obsolete.
A typical configuration would look similar to the following.
The new tunnel driver uses the gw field in the routing table
in place of the pointopoint parameter to specify the address of
the remote IPIP gateway. This is why it now supports multiple routes per
You can configure two network devices with the same address.
In this example both the sl0 and the tunl0 devices have
been configured with the IP address of the radio port. This is done so that
the remote gateway sees the correct address from your gateway in encapsulated
datagrams sent to it.
The route commands used to specify the encapsulated routes can be
automatically generated by a modified version of the munge script.
This is included below. The route commands would then be written to a separate
file and read in using the bashsource /etc/ipip.routes
command (assuming you called the file with the routing commands
/etc/ipip.routes) as illustrated. The source file must be in the
NOS route command format.
Note the use of the window argument on the
route command. Setting this parameter to an
appropriate value improves the performance of your radio link.
The new tunnel-munge script:
# From: Ron Atkinson <email@example.com>
# This script is basically the 'munge' script written by Bdale N3EUA
# for the IPIP daemon and is modified by Ron Atkinson N8FOW. It's
# purpose is to convert a KA9Q NOS format gateways route file
# (usually called 'encap.txt') into a Linux routing table format
# for the IP tunnel driver.
# Usage: Gateway file on stdin, Linux route format file on stdout.
# eg. tunnel-munge < encap.txt > ampr-routes
# NOTE: Before you use this script be sure to check or change the
# following items:
# 1) Change the 'Local routes' and 'Misc user routes' sections
# to routes that apply to your own area (remove mine please!)
# 2) On the fgrep line be sure to change the IP address to YOUR
# gateway Internet address. Failure to do so will cause serious
# routing loops.
# 3) The default interface name is 'tunl0'. Make sure this is
# correct for your system.
echo "# IP tunnel route table built by $LOGNAME on `date`"
echo "# by tunnel-munge script v960307."
echo "# Local routes"
echo "route add -net 44.xxx.xxx.xxx netmask 255.mmm.mmm.mmm dev sl0"
echo "# Misc user routes"
echo "# remote routes"
fgrep encap | grep "^route" | grep -v " XXX.XXX.XXX.XXX" | \
split($3, s, "/")
if (n == "") n="0"
if (n == "") n="0"
if (n == "") n="0"
if (n == "") n="0"
if (s == "1") mask="184.108.40.206"
else if (s == "2") mask="192.0.0.0"
else if (s == "3") mask="220.127.116.11"
else if (s == "4") mask="240.0.0.0"
else if (s == "5") mask="248.0.0.0"
else if (s == "6") mask="252.0.0.0"
else if (s == "7") mask="254.0.0.0"
else if (s == "8") mask="255.0.0.0"
else if (s == "9") mask="255.128.0.0"
else if (s == "10") mask="255.192.0.0"
else if (s == "11") mask="255.224.0.0"
else if (s == "12") mask="255.240.0.0"
else if (s == "13") mask="255.248.0.0"
else if (s == "14") mask="255.252.0.0"
else if (s == "15") mask="255.254.0.0"
else if (s == "16") mask="255.255.0.0"
else if (s == "17") mask="255.255.128.0"
else if (s == "18") mask="255.255.192.0"
else if (s == "19") mask="255.255.224.0"
else if (s == "20") mask="255.255.240.0"
else if (s == "21") mask="255.255.248.0"
else if (s == "22") mask="255.255.252.0"
else if (s == "23") mask="255.255.254.0"
else if (s == "24") mask="255.255.255.0"
else if (s == "25") mask="255.255.255.128"
else if (s == "26") mask="255.255.255.192"
else if (s == "27") mask="255.255.255.224"
else if (s == "28") mask="255.255.255.240"
else if (s == "29") mask="255.255.255.248"
else if (s == "30") mask="255.255.255.252"
else if (s == "31") mask="255.255.255.254"
if (mask == "255.255.255.255")
printf "route add -host %s.%s.%s.%s gw %s dev tunl0\n"\
printf "route add -net %s.%s.%s.%s gw %s netmask %s dev tunl0\n"\
echo "# default the rest of amprnet via mirrorshades.ucsd.edu"
echo "route add -net 18.104.22.168 gw 22.214.171.124 netmask 255.0.0.0 dev tunl0"
echo "# the end"
Many Amateur Radio Internet gateways encapsulate AX.25, NET/ROM and ROSE in
addition to tcp/ip. Encapsulation of AX.25 frames within IP datagrams is
described in RFC-1226 by Brian Kantor. Mike Westerhof wrote an implementation
of an AX.25 encapsulation daemon for UNIX in 1991. The ax25-utils package
includes a marginally enhanced version of it for Linux.
An AXIP encapsulation program accepts AX.25 frames at one end, looks at the
destination AX.25 address to determine what IP address to send them to,
encapsulates them in a tcp/ip datagram and then transmits them to
the appropriate remote destination. It also accepts tcp/ip datagrams
that contain AX.25 frames, unwraps them and processes them as if it had
received them directly from an AX.25 port. To distinguish IP datagrams
containing AX.25 frames from other IP datagrams which don't, AXIP datagrams
are coded with a protocol id of 4 (or 94 which is now deprecated). This
process is described in RFC-1226.
The ax25ipd program included in the ax25-utils package presents itself
as a program supporting a KISS interface across which you pass AX.25 frames,
and an interface into the tcp/ip protocols. It is configured with a single
configuration file called /etc/ax25/ax25ipd.conf.
The ax25ipd program has two major modes of operation. "digipeater"
mode and "tnc" mode. In "tnc" mode the daemon is treated as though it
were a kiss TNC, you pass KISS encapsulated frames to it and it will
transmit them, this is the usual configuration. In "digipeater" mode, you
treat the daemon as though it were an AX.25 digipeater. There are subtle
differences between these modes.
In the configuration file you configure "routes" or mappings between
destination AX.25 callsigns and the IP addresses of the hosts that you
want to send the AX.25 packets too. Each route has options which will be
Other options that are configured here are:
the tty that the ax25ipd daemon will open and its speed (usually
one end of a pipe)
what callsign you want to use in "digipeater" mode
beacon interval and text
whether you want to encapsulate the AX.25 frames in IP datagrams or in
UDP/IP datagrams. Nearly all AXIP gateways use IP encapsulation, but some
gateways are behind firewalls that will not allow IP with the AXIP protocol id
to pass and are forced to use UDP/IP. Whatever you choose must match
what the tcp/ip host at the other end of the link is using.
# ax25ipd configuration file for station floyd.vk5xxx.ampr.org
# Select axip transport. 'ip' is what you want for compatibility
# with most other gateways.
# Set ax25ipd mode of operation. (digi or tnc)
# If you selected digi, you must define a callsign. If you selected
# tnc mode, the callsign is currently optional, but this may change
# in the future! (2 calls if using dual port kiss)
# In digi mode, you may use an alias. (2 for dual port)
# Send an ident every 540 seconds ...
#beacon after 540
#btext ax25ip -- tncmode rob/vk5xxx -- Experimental AXIP gateway
# Serial port, or pipe connected to a kissattach in my case
# Set the device speed
# loglevel 0 - no output
# loglevel 1 - config info only
# loglevel 2 - major events and errors
# loglevel 3 - major events, errors, and AX.25 frame trace
# loglevel 4 - all events
# log 0 for the moment, syslog not working yet ...
# If we are in digi mode, we might have a real tnc here, so use param to
# set the tnc parameters ...
#param 1 20
# Broadcast Address definition. Any of the addresses listed will be forwarded
# to any of the routes flagged as broadcast capable routes.
broadcast QST-0 NODES-0
# ax.25 route definition, define as many as you need.
# format is route (call/wildcard) (ip host at destination)
# ssid of 0 routes all ssid's
# route <destcall> <destaddr> [flags]
# Valid flags are:
# b - allow broadcasts to be transmitted via this route
# d - this route is the default route
route vk2sut-0 126.96.36.199 b
route vk5xxx 188.8.131.52 b
route vk2abc 184.108.40.206
The "route" command is where you specify where you want your AX.25
packets encapsulated and sent to. When the ax25ipd daemon receives
a packet from its interface, it compares the destination callsign with each
of the callsigns in its routing table. If if finds a match then the ax.25
packet is encapsulated in an IP datagram and then transmitted to the host
at the specified IP address.
There are two flags you can add to any of the route commands in the
ax25ipd.conf file. The two flags are:
traffic with a destination address matching any of those on
the list defined by the "broadcast" keyword should be transmitted via
any packets not matching any route should be transmitted via
The broadcast flag is very useful, as it enables informations that is normally
destined for all stations to a number of AXIP destinations. Normally axip
routes are point-to-point and unable to handle 'broadcast' packets.
Many people like to run some version of NOS under Linux because it has
all of the features and facilities they are used to. Most of those people
would also like to have the NOS running on their machine capable of talking
to the Linux kernel so that they can offer some of the linux capabilities
to radio users via NOS.
Brandon S. Allbery, KF8NH, contributed the following information to explain
how to interconnect the NOS running on a Linux machine with the kernel
code using the Linux pipe device.
Since both Linux and NOS support the slip protocol it is possible to link
the two together by creating a slip link. You could do this by using two
serial ports with a loopback cable between them, but this would be slow
and costly. Linux provides a feature that many other Unix-like operating
systems provide called `pipes'. These are special pseudo devices that
look like a standard tty device to software but in fact loopback to another
pipe device. To use these pipes the first program must open the master
end of the pipe, and the open then the second program can open the
slave end of the pipe. When both ends are open the programs can
communicate with each other simply by writing characters to the pipes in the
way they would if they were terminal devices.
To use this feature to connect the Linux Kernel and a copy of NOS, or some
other program you first must choose a pipe device to use. You can find one
by looking in your /dev directory. The master end of the pipes are
named: ptyq[1-f] and the slave end of the pipes are known as:
ttyq[1-f]. Remember they come in pairs, so if you select
/dev/ptyqf as your master end then you must use /dev/ttyqf
as the slave end.
Once you have chosen a pipe device pair to use you should allocate the master
end to you linux kernel and the slave end to the NOS program, as the Linux
kernel starts first and the master end of the pipe must be opened first.
You must also remember that your Linux kernel must have a different IP address
to your NOS, so you will need to allocate a unique address for it if you
You configure the pipe just as if it were a serial device, so to create
the slip link from your linux kernel you can use commands similar to the
In this example the Linux kernel has been given IP address 220.127.116.11
and the NOS program is using IP address 18.104.22.168. The
route command in the last line simply tells your linux kernel to route
all datagrams for the amprnet via the slip link created by the
slattach command. Normally you would put these commands into your
/etc/rc.d/rc.inet2 file after all your other network configuration
is complete so that the slip link is created automatically when you reboot.
Note: there is no advantage in using cslip instead of slip
as it actually reduces performance because the link is only a virtual
one and occurs fast enough that having to compress the headers first takes
longer than transmitting the uncompressed datagram.
To configure the NOS end of the link you could try the following:
# you can call the interface anything you want; I use "linux" for convenience.
attach asy ttyqf - slip linux 1024 1024 38400
route addprivate 22.214.171.124 linux
These commands will create a slip port named `linux' via the slave end of
the pipe device pair to your linux kernel, and a route to it to make it
work. When you have started NOS you should be able to ping and telnet to
your NOS from your Linux machine and vice versa. If not, double check that
you have made no mistakes especially that you have the addresses configured
properly and have the pipe devices around the right way.