DYNAMIC ROUTING PROTOCOL

DYNAMIC ROUTING PROTOCOL

 DYNAMIC ROUTING PROTOCOL

It is the routing in which the routing table entries are updated automatically by the routing protocol. It performs the same function as static routing except it is more robust. If a router on the route goes down the destination may become unreachable. Dynamic routing allows routing tables in routers to change as the possible routes change.

Dynamic routing protocols do not change how routing is done. They just allow for dynamic altering of routing tables.
There are two classifications of protocols:

    1. IGP – Interior Gateway Protocol. Used for routing inside an autonomous system & used to route within the individual networks themselves. E.g. RIP, EIGRP, OSPF.

  2. EGP – Exterior Gateway Protocol. Used for routing between autonomous systems. E.g. BGPv4.

Autonomous system: A collection of networks under a common administration sharing a common routing strategy.

We make use of IGPs to resolve routes within an AS. The interior gateway protocolscan be divided into two categories:

A.   Distance-vector routing protocol

B.   Link-state routing protocol.

 A.   Distance-vector routing protocol:

Distance-vector routing protocols use the Bellman-Ford algorithm. In these protocols, each router possesses incomplete information about the network topology. It advertises its distance value (DV) calculated to other routers and receives similar advertisements from other routers unless changes are done in local network or by neighbors (Routers). The updates are generally periodic.

E.g. RIP, EIGRP (sometimes called as hybrid routing protocol)

B.   Link-state routing protocol

A routing protocol in which routers exchange information with one another about the reachability of other networks and the cost or metric to reach the other networks. Link state routers use Dijkstra algorithm to calculate the shortest path to a destination and normally updates other routers with whom they are connected only when their own routing table change.

E.g. OSPF