Dynamic routing is the process of using protocols to find and update routing tables on routers. This is easier than static or default routing, but you use it at the expense of router CPU processes and bandwidth on the network links. A routing protocol defines the set of rules used by a router when it communicates between neighbor routers.
When configuring routing protocols, you need to be a aware of administrative distances (Ads).These are used to rate the trustworthiness of routing information received on a router from a neighbor router. An administrative distance is an integer from 0 to 255,where 0 is the most .
Default Administrative Distances
|Unknown||255(this route will never be used)|
Routing ProtocolsTrusted and 255 means no traffic will be passed via this route.
There are three classes of routing protocols:
Distance vector :The distance-vector routing protocols use a distance to a remote network to find the best path. Each time a packet goes through a router, it’s called a hop. The route with the least number of hops to the network is determined o be a best route. The vector is the determination of direction to the remote network. Examples of distance-vector routing protocols are RIP and IGRP.
Link state : Typically called shortest path first, the routers each create three separate tables. One of these tables keeps track of directly attached neighbors, one determines the topology of the entire internetwork, and one is used for the routing table. Link -state routers know more about the internetwork than any distance-vector routing protocol. An example of an IP routing protocol that is completely link state is OSPF.
Hybrid : Uses aspects of distance vector and link state, for example, EIGRP.
There is no set way of configuring routing protocols for use with every business. This is a task that is performed on a case-by-case basis. However, if you understand how the different routing protocols work, you can make good business decisions. This course and equivalent exam only cover distance-vector routing protocols and theory.
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