 Internet from router to router using routing tables. A route is a path from the sending device to the receiving device. The routing decision is based on the destination address of the packet and the routing table on the router. If the packet is addressed to a system on a network that is directly connected to the router, it will place the packet on that network segment. If it is addressed to a device on a network that is not directly connected, then it will be forwarded to an appropriate router for further routing. IP routing protocols are dynamic. Dynamic routing calls for routes to be calculated automatically at regular intervals by software in routing devices. This contrasts with static routing, where routers are established by the network administrator and do not change until the network administrator changes them. 12.8.1 ROUTING PROTOCOLS Overview A number of routing protocols are in use today, e.g. interior gateway routing protocol, (IGP), exterior gateway routing protocol, (EGP), routing information protocol (RIP), open Packet Backbone shortest path first (OSPF) and border gateway routing protocol (BGP). Once the destina- tion address is resolved the routers determine the best way to reach that address through a network of nodes. Routing algorithms are used to exchange information about the network topology. When distance vector routing algorithms are used each router builds and maintains its own routing table (a vector) that gives the best-known distance to each destination in the network and how to get there. These tables are updated by periodically exchanging information with their neighbours. In link state routing algorithms each router learn the link state in the whole network. This is achieved by flooding the link state changes via the entire network. Flooding means that the information is copied from node to node in a tree structure. Each router builds its own forwarding table from its own perspectives. Routing Information Protocol (RIP) The RIP is a relatively old, but widely used interior gateway 