Routing Protocol: EIGRP

Enhanced Interior Gateway Routing Protocol (EIGRP) is a classless, enhanced distance vector and Cisco proprietary routing protocol. Like RIP, EIGRP is based on a distance vector algorithm that determines the most beneficial path to a destination. It uses the concept of autonomous system to describe the network of routers that run the same routing protocol and share the identical information.

EIGRP can also be referred to as a hybrid routing protocol, this is simply because it possess the characteristic of both distant vector and link state protocols. Routing protocols like OSPF sends link-state packets but, EIGRP sends conventional distance vector updates which carries facts about networks and the expense to reach them. It's link state characteristic consists of synchronization of routing tables with neighbouring routers at commence up and sending of updates only when changes happen in the topology. By default, EIGRP produce equal-expense load balancing of up to 4 links, but as a network administrator you can load balance across up to six links.

EIGRP utilizes a even more complicated metric than RIP's basic hop count. It has a maximum hop count of 255 (default is 100). This makes it appropriate for huge networks. The metric use by EIGRP is based on the minimum bandwidth and net delay along every single doable path, which means that EIGRP can accommodate larger networks than RIP. It also means that EIGRP needs a completely different algorithm for loop removal, given that EIGRP cannot merely increment the hop count to infinity to eradicate a loop.

Other characteristic of EIGRP, consists of the listing of subnet masks in its routing updates, which indicates that, as an administrator, you are allowed to use Variable Length Subnet Mask (VLSM) and route summarization.

The most impressive function of EIGRP is its capacity to deliver routing support for multiple network layer protocols which includes IP, IPX, Apple Speak and IPv6.

EIGRP makes use of a protocol known as Reliable Transport Protocol (RTP) to manage communication in between routers in a network. EIGRP sends multicast site visitors applying the class D 224...10, if any of the neighbours does not reply, it will then send a unicast message in an try to send the identical data to a neighbour.

To maintain neighbour establishment relationship:

i. EIGRP router have to send and receive a "Hello and ACK".

ii. Their AS (autonomous technique) number should match

iii. There have to be identical metrics (K value)

Attributes of EIGRP

i. Classless routing protocol

ii. Supports VLSM and CIDR

iii. Assistance for IPv4 and IPv6

iv. Selects the greatest achievable portion utilizing Diffusing Update Algorithm - DUAL