From Linux Journal: "In the 2.4.X kernels, Rusty Russell, the Linux packet-filter guru, and his crew of coders have implemented Netfilter into the kernel. Netfilter is the replacement
for ipchains or ipfwadm. Fortunately, Netfilter permits you to keep using ipchains or ipfwadm until you can come to grips with iptables by adding a
compatibility layer via a kernel module that permits these older packet filters to run. But Netfilter has so many exciting new additions, you'll want to convert
those rules as soon as possible. One word of caution, though, if you load the ipchains or ipfwadm modules, you can't load ip_tables (and vice versa). So it's
all or nothing. After reading this article, however, making the change should be easy."
August 27, 2001