Packet Filtering and Packet Mangling with Your Router
In addition to using your Linux box to perform routing tasks, you might want to set it up to do some other kinds of packet filtering. There are two packages that we’ll take a look at in this section: the ipchains package and Netfilter/ iptables.
The ipchains package is a little more limited than Netfilter/ iptables, but if you’re using the 2.2.x series of the kernel, then you’re limited to ipchains—at least until someone backports them to 2.2.x. If you’re already well-versed in writing rules for ipchains but want to upgrade to the 2.4.x series, you’ll be happy to know that there is an ipchains compatibility module for 2.4.x.
What is Packet Filtering?
As you’re already aware, all this networking ...