Router are networking devices much like a normal PCs but functions to connection multiple networks and the mail role is to forward packets (best path) form one network to the next. Router consists of CPUs, RAM,ROM and an operating systems. Router consists of multiple interfaces to connect to multiple networks.  Router also maintains a routing table, which is a list of networks known by the router. The routing table includes network addresses for its own interfaces, which are the directly connected networks, as well as network addresses for remote networks.

Routing table can be added in two ways: either by the network administrator manually configuring static routes or by implementing a dynamic routing protocol.

1. Static Routing.

Static Routing is manually configuring a route on a router to reach a specific destination network. It is use full for small networks. Static routes can require more maintenance if the topology is constantly changing or is unstable.

2. Dynamic Routing

Dynamic routing protocols automatically adjust to changes without any intervention from the network administrator. It can determine the best path to the destination. Dynamic routing protocols require more CPU processing and also use a certain amount of link capacity for routing updates and messages

Routing can also be divided into following

  • Interior Gateway Protocol (!GP)

             IGP are used for intra-autonomous system routing [ routing inside an autonomous system].

Eg:   Routing Information Protocol (RIP), Open Shortest Path First (OSPF), Interior Gateway Routing Protocol (IGRP), Enhanced Interior Gateway Routing Protocol (EIGRP), Intermediate System to Intermediate System (IS-IS)

  • Exterior Gateway Protocol (EGP)

            EGP are used for inter-autonomous system routing – [routing between autonomous systems].

Eg: Border Gateway Protocal (BGP)