Preamble

Despite the age of this document, the contents continue to be very relevant even now in the mid 2020's and the need for packet filtering is not going away anytime soon. According to the Netfilter main page, the project continues with updates still being applied to iptables. Nevertheless, the site also indicates that iptables has a successor product called nftables. To quote the site "The netfilter project is commonly associated with iptables and its successor nftables."

So, should I read this document? The answer is an emphatic "Yes!". There is no doubt that in your networking career that you will come across iptables, and this document contains the background needed to understand the underlying filtering technology, as well as how to read and understand the iptables rulesset.

Most of the knowledge in this document is directly applicable to nftables. It has a newer command syntax that is supposed to be easier to use. In summary, if you need to modify or extend the iptables rules on a system, then by all means, it's probably wise to make your revisions using iptables. However, if you are setting up filtering on a server that does not yet have any filtering, considering to use nftables would be worth looking into.