Entire Linux Network stack diagram (2024)

This place needs more of this kind of documentation.

I failed to use IP tables for years. I bought books. I copied recipes from blog posts. Nothing made sense, everything I did was brittle. Until I finally found a schematic showing the flowchart of a packet through the kernel, which gives the exact order that each rule chain is applied, and where some of the sysctl values are enforced. All of a sudden, I could write rules that did exactly what I wanted, or intelligently choose between rules that have equivalent behaviors in isolation but which could have different performance implications.

After studying the schematic, every would just work on the first try. A good schematic makes a world of difference!

Can you share the diagram? Would love to become iptables-enlightened.

It is time to be nftables enlightened instead.

It's more of a netfilter (the thing behind iptables and nftables) diagram rather than just iptables.

If you know how iptables maps to that diagram you are very likely to be able to quickly understand how nftables does too.

Sure, but we really shouldn’t be encouraging the use of iptables in 2025.

That's not realalistic for most of the Linux world.

Soooo many systems are still using iptables even though we "should" be using nft everywhere.

If you're going to be a Linux Sys/Net Admin today, you need an understanding of both systems.

If someone doesn’t know iptables, they probably are not required to know it. You wouldn’t recommend people to learn C++03, would you?