The IPexpert Blog » IPexpert to Announce Dynamips Support and “Everything IE” Private Beta Launch. NAT Order of Operation [IP Addressing Services. Introduction This document illustrates that the order in which transactions are processed using Network Address Translation (NAT) is based on whether a packet goes from the inside network to the outside network, or from the outside network to the inside network.
Prerequisites Requirements Readers of this document should have knowledge of this topic: Network Address Translation (NAT). PacketLife.net. Using Linux iptables or ipchains to set up an internet gateway / firewall / routerfor home or office. Note: References to ipfwadm and ipchains refer to older deprecated software.
Note: Red Hat 7.1-9.0 and the default Linux 2.4 kernel may use ipchains or iptables but not both. Iptables is the preferred firewall as it supports "state" and can recognize if a network connection has already been "ESTABLISHED" or if the connection is related to the previous connection (required for ftp which makes multiple connections on different ports). Ipchains can not. Ipchain rules take precedence over iptables rules. During system boot, the kernel attempts to activate ipchains, then attempts to activate iptables.