The AX.25 software is comprised of three components, the kernel source, the network configuration tools and the utility programs.
The version 1.3.xx Linux kernels include the AX.25, NetRom, Z8530 SCC, PI card and PacketTwin drivers by default. I recommend you obtain and use the version 1.3.xx kernel source.
These are three reasons I'm recommending you use the alpha version software even though most everyone else will recommend you don't use it:
Be warned though, this software is alpha and may have problem that you wouldn't otherwise encounter. Please take all the usual precautions and be sure to keep a working kernel as backup when testing new kernels. It is wise to test a new kernel by booting from it from floppy before actually installing it with lilo, though I haven't bothered for about 90 kernels revisions so I'm fairly confident you can pretty safely run with alpha kernels.
The kernel source can be found in its usual place at:
ftp.funet.fi
/pub/Linux/PEOPLE/Linus/v2.0/
The latest alpha release of the standard Linux network tools support AX.25 and NetRom and can be found at:
ftp.inka.de
/pub/comp/Linux/networking/net-tools/net-tools-1.32-alpha.tar.gz
or:
ftp.linux.org.uk
/pub/linux/Networking/PROGRAMS/NetTools/net-tools-1.32-alpha.tar.gz
The latest ipfwadm package can be found at:
ftp.xos.nl
/pub/linux/ipfwadm/
The AX.25 utility programs can be found at:
sunsite.unc.edu
/pub/Linux/apps/ham/ax25-utils-2.0.0.tar.gz
or:
ftp.ucsd.edu
/hamradio/packet/tcpip/incoming/ax25-utils-2.0.0.tar.gz