Enhanced Interior Gateway Routing Protocol (EIGRP)

nhanced Interior Gateway Routing Protocol (EIGRP) is an distance-vector routing protocol and is used on networks for automating routing decisions and configuration. The EIGRP was designed by Cisco Systems as a proprietary protocol, available only on Cisco routers. Partial functionality of EIGRP was converted to an open standard in 2013.

EIGRP is used on a router to share routes with other routers within the same autonomous system (AS). Unlike RIP, EIGRP only sends incremental updates, reducing the workload on the router and the amount of data that needs to be transmitted.

EIGRP replaced the Interior Gateway Routing Protocol (IGRP) in 1993. One of the major reasons for this was the change to classless IPv4 addresses in the Internet Protocol, which IGRP could not support.


EIGRP supports the following features:

  • Support for Classless Inter-Domain Routing (CIDR) and variable length subnet masking.
  • Support for load balancing on parallel links between sites.
  • The ability to use different authentication passwords at different times.
  • MD5 and SHA-2 authentication between two routers.
  • Sends topology changes only.
  • Periodically checks if a route is available, and propagates routing changes to neighboring routers if any changes have occurred.
  • Runs separate routing processes for Internet Protocol (IP), IPv6, IPX and AppleTalk, through the use of protocol-dependent modules (PDMs).
  • Backwards compatibility with the IGRP routing protocols.

Cisco IOS example

The wildcard in this example indicates a subnetwork with a maximum of 254 hosts.

 R1# configure terminal
 R1(config)# router eigrp 2
 R1(config-router)# network
 R1(config-router)# no auto-summary
 R1(config-router)# exit