iptables: administration tool for packet filtering and NAT

iptables is a command line utility for configuring Linux kernel firewall implemented within the Netfilter project. The term iptables is also commonly used to refer to this kernel-level firewall. It can be configured directly with iptables, or by using one of the many console and graphical front-ends. iptables is used for IPv4 and ip6tables is used for IPv6. Both iptables and ip6tables have the same syntax, but some options are specific to either IPv4 or IPv6.