[ ROUTER ] Routing Protocols And Types of Routing?

Routing Protocols And Types of Routing?

Routing Protocols

Routing protocols were created for routers. These protocols have been designed to allow the exchange of routing tables, or known networks, between routers. There are a lot of different routing protocols, each one designed for specific network sizes.

Two main types of routing:

1:Static routing

2: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 (administrator manually enters the routes in the router's table) or dynamic routing (happens automatically using routing protocols like EIGRP,OSPF,etc.).

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:

Routing Protocols
Features	RIPv1	RIPv2	IGRP	OSPF	EIGRP
Classful/Classless Metric Time Period Administrative Distace(AD) Type	Classful Hop 30 sec 120 Distance vector	Classless Hop 30 sec 120 Distance vector	Classful Composite (90 sec) 90 sec 100 Distance vector	Classless Cost None 110 Link state	Classless Composite (30 sec) 30 sec Internal:  90 External: 170 Hybrid

You can also classify the routing protocols in terms of their location on a network. For example, routing protocols can exist in, or between, autonomous systems.