7. Configuring an AX.25 interface for TCP/IP

It is very simple to configure an AX.25 port to carry TCP/IP. If you have KISS interfaces then there are two methods for configuring an IP address. The kissattach command has an option that allows you to specify an IP address. The more conventional method using the ifconfig command will work on all interface types.

So, modifying the previous KISS example:

# /usr/sbin/kissattach -i -m 512 /dev/ttyS0 radio
# /sbin/route add -net netmask ax0
# /sbin/route add default ax0

to create the AX.25 interface with an IP address of and an MTU of 512 bytes. You should still use the ifconfig to configure the other parameters if necessary.

If you have any other interface type then you use the ifconfig program to configure the ip address and netmask details for the port and add a route via the port, just as you would for any other TCP/IP interface. The following example is for a PI card device, but would work equally well for any other AX.25 network device:

# /sbin/ifconfig pi0a netmask up
# /sbin/ifconfig pi0a broadcast mtu 512
# /sbin/route add -net netmask pi0a
# /sbin/route add default pi0a

The commands listed above are typical of the sort of configuration many of you would be familiar with if you have used NOS or any of its derivatives or any other TCP/IP software. Note that the default route might not be required in your configuration if you have some other network device configured.

To test it out, try a ping or a telnet to a local host.

# ping -i 5

Note the use of the `-i 5' arguments to ping to tell it to send pings every 5 seconds instead of its default of 1 second.