Dynamic Routing

Dynamic Routing

Dynamic routing is when protocols are used to find networks and update routing tables on routers.

 A routing protocol defines the set of rules used by a router when it communicates routing information between neighbour routers.

Routing Protocols

RIP

EIGRP

OSPF

IS-IS

BGP

Routing Protocol Basics

There are some important things you should know about routing protocols before getting

deeper into RIP. Specifically, you need to understand administrative distances, the three different

kinds of routing protocols, and routing loops. We will look at each of these in more detail

in the following sections.

Administrative Distances

The administrative distance (AD) is used to rate the trustworthiness of routing information

received on a router from a neighbour router. An administrative distance is an integer from 0 to

255, where 0 is the most trusted and 255 means no traffic will be passed via this route.

If a router receives two updates listing the same remote network, the first thing the router

checks is the AD. If one of the advertised routes has a lower AD than the other, then the route

with the lowest AD will be placed in the routing table.

 The advertised route with the lowest metric will be placed in the routing table. But if

both advertised routes have the same AD as well as the same metrics, then the routing protocol

will load-balance to the remote network.

Default Administrative Distances

Connected interface                       0

Static route                                     1

EIGRP                                            90

IGRP                                              100

OSPF                                              10

RIP                                                 120

External EIGRP                             170

Unknown                                       255 (Invalid Route)