3.3.n Implement and troubleshoot routing protocol authentication

3.3.n [ii] Key-chain

Key chains consist of two mandatory and two optional components. The necessary components are key number and key string. Optionally it also include an accept-lifetime and a send-lifetime parameter.

Key chain configuration steps:

● First you need to configure key chain in global configuration mode.

● Under key chain you need to configure key number. Key number must be match on both side of router and should be active. If multiple key numbers are configured on a router , the router will select the lowest key ID number for outbound authentication however will accept any matching valid keys in the keychain upon receipt

● Once you configure key number you need to issue authentication string

Adam, Paul (2014-07-12). All-in-One CCIE V5 Written Exam Guide (Kindle Locations 2880-2881).  . Kindle Edition.

http://www.cisco.com/c/en/us/td/docs/ios/iproute_eigrp/command/reference/ire_book/ire_i1.pdf