Monday, 26 October 2015
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 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.
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
External EIGRP 170
Unknown 255 (Invalid Route)