How to configure authentication for EIGRP, a Cisco proprietary enhanced distance vector routing protocol

Cisco How-To Tutorials
Enhanced Interior Gateway Routing Protocol (EIGRP) is a Cisco proprietary enhanced distance vector routing protocol. EIGRP provides benefits like fast convergence, incremental updates and support for multiple network layer protocols. EIGRP supports Message Digest 5 (MD5) authentication to prevent malicious and incorrect routing information from being introduced into the routing table of a Cisco router. To configure EIGRP authentication, the keys used in the authentication process have to be configured and attached to an interface along with MD5 as the mode of authentication. To configure authentication, apart from the basic steps required for enabling EIGRP, perform these steps:

1. To configure the keys, identify a group of authentication keys by issuing the key chain name-of-chain command in global configuration mode.
2. To identify an authentication key on a key chain, issue the key key-id command in key-chain configuration mode.
3. To specify the key authentication string, issue the key-string text command in key-chain key configuration mode.
4. To enable authentication for EIGRP packets and to specify the set of keys to be used on an interface, issue the ip authentication key-chain eigrp as-number key-chain command in interface configuration mode.
5. To specify MD5 as the type of authentication to be used for EIGRP packets, issue the ip authentication mode eigrp as-number md5 command in interface configuration mode. EIGRP does not support plain text authentication.
6. Optionally, you can configure key management to automatically migrate from one authentication key to another by configuring the accept-lifetime start-time {infinite | end-time | duration seconds} and send-lifetime start-time {infinite | end-time | duration seconds} commands in key-chain key configuration mode.

For further information on configuring EIGRP authentication with an example you may wish to refer to: Cisco Configuring EIGRP

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