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Routing & Switching · Intermediate

Key Chain

A Cisco construct holding one or more numbered keys with optional lifetimes, used for routing protocol authentication.

Definition

EIGRP, RIPv2, OSPF (HMAC-SHA) and IS-IS reference key chains. Multiple keys with overlapping accept and send lifetimes allow hitless key rollover. Key IDs must match on both ends for EIGRP.

Example

key chain EIGRP-KEYS / key 1 / key-string Cisco123

Exam tip

In EIGRP the key number and string must both match; a stray trailing space in key-string breaks authentication.

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