Traffic Rules

Whether you are training to become an IT specialist, managing networks, or preparing for the Linux Professional Institute second certification (LPIC-2) [1], you can't avoid the topic of firewalls, especially rules for filtering packets on the network. After ipchains and Ipfw, the netfilter project's [2] iptables is mostly commonly used for configuring firewall rules on Linux, while FreeBSD/NetBSD and the two Solaris successors Illumos and OpenIndiana use IPFilter [3].

However, iptables is getting a little long in the tooth. In particular, the program code has become increasingly complex. Small changes in the project core have tended to affect all related tools. Iptables, ip6tables, ebtables, and arptables all come from the same codebase, but not in the form of modules. Instead they rely on code duplication, which has resulted in the four tools drifting apart over time. Iptables has been the best maintained, while ebtables has been neglected. Bugs fixed in iptables are still unfixed in ebtables years later.

This situation prompted the netfilter project to launch the development of an iptables successor, nftables [4], as early as 2009. The first two letters in nftables are derived from the project (netfilter). The stated development goals include higher data throughput, greater scalability with a view to changing requirements, and – in particular – a modular structure leading to improved maintainability [5]. Starting with Linux 3.13 (January 2014), nftables is part of the Linux kernel [6], using proven in-house components by the netfilter project.

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