An algorithm is a mathematical process used to arrive at a particular solution. It is repeatable; that is, using the same input, one will get the same output. With respect to routing protocols, the algorithm can be thought of as the set of rules or process that the routing protocol uses to determine the desirability of paths on the internetwork for the movement of packets. The router uses the routing algorithm to build the routing table the router uses as it forwards packets. Routing algorithms come in two basic .avors, based on how they calculate routes: static and dynamic. Static algorithms consist of internetwork mapping information that a network administrator enters into the router’s routing table. This table dictates how packets are moved from one point to another on the network. All routes on the network are static; that is, unchanging. Static routes are preferable for routes coming into and out of a router used as part of a firewall configuration.