This tutorial is pretty old actually. Hope someone updates it, then we have nftables on the way to replace iptables, so might be just update to nftables directly.

I found 'nft', along with other commands such as 'ip' and 'tc' are pretty hard to use. I hope someone can create all possible auto-completion to guide the users, it is so hard to memorize those abbrev tags/options for those commands.