Multi-homed host

A multi-homed host is a host (a firewall in this case) that has more than one network interface, with each interface connected to logically and physically separate network segments. A dual-homed host (host with two interfaces) is the most common instance of a multi-homed host.

A dual-homed firewall is a firewall with two network interfaces cards (NICs), with each interface connected to a different network. For instance, one network interface is typically connected to the external or untrusted network, whereas the other interface is connected to the internal or trusted network. In this configuration, a key security tenet does not allow traffic coming in from the untrusted network to be directly routed to the trusted network, and the firewall must always act as an intermediary.

Tip: Routing by the firewall is usually disabled for a dual-homed firewall so that Internet Protocol (IP) packets from one network are not directly routed from one network to the other.