Take the version of ipfwadm that works for your Linux kernel:

Linux 1.2.1 - 1.2.13
	ipfwadm 1.2

Linux 1.3.66 and newer (including Linux 2.0.0 and above!)
	ipfwadm 2.3.0

For both versions you can find RPM files for use with Red Hat Linux.

In the old directory you can find some old versions of ipfwadm.
In a few cases you might need one of them:

Linux 1.3.1 - 1.3.60
	ipfwadm 1.2 may work for SOME of the 1.3.x kernels,
	but officially these versions are not supported

Linux 1.3.61 - 1.3.65
	ipfwadm 2.0beta1

The file "patch-1.3.66-masq" contains a very small patch for
Linux 1.3.66 which solves a bug in the IP masquerading code.
Linux 1.3.67 and above do NOT need this patch.