Distance Vector Routing Protocol

Distance Vector Routing Protocol, as the name implies,
Distance : how far the destination from this router.
Vector     : the direction to forward the packet to the destination
DV RP doesn't know the full path to reach the destination, it only know how far the destination is, and the direction of the destination.

Terminology
Split Horizon - that a router should not advertise a network through the interface from which the update came.
Poison routing - a way for DV router to make a route removed from a table of neighboring router by making the metric of the route to be unreachable.

RIP
Routing Information Protocol (RIP) was originally specified in RFC 1058. It has the following key characteristics:
- Hop count is used as the metric for path selection.
- If the hop count for a network is greater than 15, RIP cannot supply a route to that network.
- Routing updates are broadcast or multicast every 30 seconds, by default.


EIGRP
Enhanced IGRP (EIGRP) is a Cisco proprietary distance vector routing protocol. EIGRP has these key characteristics:
- It can perform unequal cost load balancing.
- It uses Diffusing Update Algorithm (DUAL) to calculate the shortest path.
- There are no periodic updates as with RIP and IGRP. Routing updates are sent only when there is a change in the topology.