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Routing Table Overview

Typically, routers are attached to multiple networks and are responsible for directing traffic across these networks. Each router maintains a routing table, which is a list of known networks and directions on how to reach them. While processing an incoming packet on a security device, the router performs a routing table lookup to find the appropriate interface that leads to the destination address.

Each entry in a routing table—called a route entry or route—is identified by the destination network to which traffic can be forwarded. The destination network, in the form of an IP address and netmask, can be an IP network, subnetwork, supernet, or a host. Routing table entries can originate from the following sources:

  • Directly connected networks (the destination network is the IP address that you assign to an interface in Route mode)

  • Dynamic routing protocols, such as OSPF, BGP, or RIP

  • Routes that are imported from other routers or virtual routers

  • Statically configured routes

You can configure three types of static routes: destination-based, source-based, and source-interface-based routing. For each type of static route, you configure the following information:


Source-interface-based routing is supported in ScreenOS 5.1 and later.

  • The interface on the security device on which traffic for the destination network is forwarded.

  • The next-hop, which can be either another virtual router on the security device or a gateway IP address (usually a router address).

  • The protocol from which the route is derived.