Enhanced Interior Gateway Routing Protocol (EIGRP)
Enhanced Interior Gateway Routing Protocol is an advanced distance vector dynamic routing protocol using bandwidth and delay metrics to establish optimum forwarding paths.
- The Interior Gateway Routing Protocol (IGRP) was developed by Cisco to provide a routing protocol for routing within a domain or autonomous system.
- limitations led to the development of Enhanced IGRP (EIGRP)
- e.g., lack of support for classless addressing
- versions for IPv4 and IPv6
- EIGRP is a distance vector protocol because it relies on neighboring routers to report paths to remote networks
- like RIP
- uses a metric composed of administrator weighted elements
- unlike RIP, which uses a simple hop count metric
- two default elements:
- bandwidth
- applies a cost based on the lowest bandwidth link in the path
- delay
- applies a cost based on the time it takes for a packet to traverse the link
- this is most important if the route is used to carry time-sensitive data
- e.g., voice or video
- calculated as the cumulative value for all outgoing interfaces in the path
- bandwidth
- sends a full update when it first establishes contact with a neighbor and thereafter, only sends updates when there is a topology change
- unlike RIP which sends periodic updates of its entire routing info base
- more efficient and less disruptive to large networks
- gives best convergence performance in many scenarios
- uses regular hello messaging to confirm connectivity with its neighbors
- maintains a topology table alongside its routing information base
- unlike RIP, which does not
- used to prevent loops while also supporting a greater number of maximum hops than RIP (up to 255)
- is a default IP protocol
- means that it is encapsulated directly in IP datagrams, rather than using TCP or UDP
- tagged with protocol number 88 in the Protocol field of the IP header
- updates are transmitted using multicast addressing