Before we begin discussing EIGRP, we need to understand where it came from. It originated from Interior Gateway Routing Protocol (IGRP). The problem with IGRP is that it had no support for Variable Length Subnet Masking (VLSM) and it was broadcast-based. With the Enhance Interior Gateway Routing Protocol, we now have support for VLSM and the updates are sent via a multicast using the following multicast address: 224.0.0.100 for IPv4.
EIGRP has a lot more to offer than its predecessor. Not only is it a classless routing protocol with VLSM capabilities, it has a maximum hop count of 255, but by default this is set to 100. It is also considered a hybrid or advanced distance-vector routing protocol. That means that it has the better of two worlds, with a links state and distance vector (DV). The DV features are just like RIPv2, where it has limited hop...
