Learning OpenStack Networking - Third Edition

An introduction to iptables

Iptables is a firewall built into Linux that allows a system administrator to define tables containing chains of rules that determine how network packets should be treated. Packets are processed by sequentially traversing rules in chains within the following tables:

• Raw: This is a default table that filters packets before any other table. It is mainly used for rules related to connection tracking.
• Filter: This is a default table for filtering packets.
• NAT: This is a default table used for network address translation.
• Mangle: This is a default table used for specialized packet alteration and is not used by the Security Group API.

A rule in a chain can cause a jump to another chain, which, in turn, can jump to ...