The five default chains include the following: There are five default chains, and the origin of the packet determines which chain will be initially traversed. When iptables is enabled, every network packet arriving at or leaving an interface traverses at least one chain. If the traffic does not match the rules of a subchain, the system recalls the point at which the jump occurred and returns to that point for further processing. This behavior can be repeated to whatever level of nesting is desired. Mangle: This is a default table used for specialized packet alteration and is not used by the Security Group API.Ī rule in a chain can cause a jump to another chain, which, in turn, can jump to another chain, and so on. NAT: This is a default table used for network address translation. It is mainly used for rules related to connection tracking.įilter: This is a default table for filtering packets. Raw: This is a default table that filters packets before any other table. Packets are processed by sequentially traversing rules in chains within the following tables: 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. In this article I will take you through 30 most popular iptables commands in Linux. Check Other Options with iptables command To Zero out the Counter for all Chain and Rules Reject TCP Packets with ICMP PORT UNREACHABLE Message To Limit the Number of Concurrent Connections To block outbound tcp traffic to IP 192.168.0.106
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