Routing Protocols

Routing is the process of sending data from one end to the other. While doing this you need to select the best or the shortest path for sending data to the node from one point to the other.

There are a lot of different routing protocols, each one designed for specific network sizes.

Two main types of routing:

 Static routing

 Dynamic routing

The router learns about remote networks from neighbor routers or from an administrator. The router then builds a routing table. If the network is directly connected then the router already knows how to get to the network.

If the networks are not attached, the router must learn how to get to the remote network with either static routing or dynamic routing

The routers then update each other about all the networks they know. If a change occurs e.g a router goes down, the dynamic routing protocols automatically inform all routers about the change. If static routing is used, then the administrator has to update all changes into all routers and therefore no routing protocol is used.

Only Dynamic routing uses routing protocols, which enable routers to:

• Dynamically discover and maintain routes
• Calculate routes
• Distribute routing updates to other routers
• Reach agreement with other routers about the network topology

Statically programmed routers are unable to find  routes, or send routing information to other routers. They send data over routes defined by the network Admin.

A Stub network is so called because it is a dead end in the network. There is only one route in and one route out and, because of this, they can be reached using static routing, thus saving valuable bandwidth.

Dynamic Routing Protocols

There are 3 types of Dynamic routing protocols, these are differ by  the way that discover and make calculations about routes;

1. Distance Vector

2. Link State

3. Hybrid

• Distance Vector routers find the best path from information send from neighbors
• Link State routers each have a copy of the entire network map
• Link State routers find best routes from this local map

The Table below shows the main characteristics of a few different types of dynamic routing protocols: