Implementation of Iptables in Linux (1)

LinuxSystemIptablesThe implementation of the terminal is described as follows:

Preparation: iptable has three groups (tables), mangle queue, filter queue, and nat queue.

1. The first is the mangle table which is responsible for the alteration of quality of service bits in the TCP header.

2. The second table is the filter queue which is responsible for packet filtering.

* Forward chain: Filters packets to servers protected by the firewall.

* Input chain: Filters packets destined for the firewall.

* Output chain: Filters packets originating from the firewall.

3. The third table is the nat queue which is responsible for network address translation. It has two built-in chains; these are:

* Pre-routing chain: NATs packets when the destination address of the packet needs to be changed.

* Post-routing chain: NATs packets when the source address of the packet needs to be changed