Iptables

iptables is a packet filtering, NAT/PAT and packet mangling tool for Linux. Used by a variety of Linux distributions including Ubuntu, Redhat and CentOS. Iptables is highly configurable and are used in many firewall solutions.

Using IPTABLES

Iptables is a commandline command with numerous options, and need some training to master. Basically iptables has three chain.s

• forward: Packets traversing from one Interface to another Interface
• input  : Packets from a Interface to a local process on the machine. A packet from outside to the machine.
• output : Packets from a local process - the machine itself - to the outside world.

iptables flowchart showing chains