Distance Vector
- Router will advertise a route as a vector of direction and distance.Direction refers to a port that leads to the next router along the path to the destination, and distance is a metric that indicates the number of hops to the destination
- Distance Vector protocols determine best path on how far the destination is.
- Examples of distance-vector routing protocols include RIPv1 and 2 and IGRP.
- EGP and BGP are not pure distance-vector routing protocols but their concepts are the same. In many cases, EGP and BGP are considered DV (distance-vector) routing protocols.
- A distance-vector routing protocol requires that a router informs its neighbors of topology changes periodically and, in some cases, when a change is detected in the topology of a network.
- Distance-vector routing protocols are simple and efficient in small networks, and require little, if any management.
Link-state
- Examples of link-state routing protocols include OSPF and IS-IS.
- The basic concept of link-state routing is that every node constructs a map of the connectivity of the network, in the form of a graph showing which nodes are connected to which other nodes.
- The link-state routing requires each switching node in the network to send its information about its neighbours to the entire internetwork.
- Each node then independently calculates the best next hop from it for every possible destination in the network. (It does this using only its local copy of the map, and without communicating in any other way with any other node.) The collection of best next hops forms the routing table for the node.
- This contrasts with distance-vector routing protocols, which work by having each node share its routing table with its neighbors. In a link-state protocol, the only information passed between the nodes is information used to construct the connectivity maps.