I'm trying to find something out. I want to know if you need to have the same key ID with EIGRP between two interfaces that are authenticating with each other.
E.g. - you use MD5 authentication to secure EIGRP. You then choose an MD5 pre-shared key and this is associated with a key ID that you have to choose, i.e. 1. It is not clear within Cisco documentation as to whether this key ID has to be the same at both ends.
With OSPF, the key ID definitely has to be the same at both ends - http://www.cisco.com/en/US/docs/ios_xr_sw/iosxr_r3.0/routing/configuration/guide/rc3ospf.html -
"message-digest-key key-id md5 [encryption-type] key
message-digest-key 4 md5 0 yourkey
Specifies the MD5 authentication key for the OSPF process.
â¢Your neighbor router must have the same key identifier."
I'd appreciate confirmation, preferably with a source to confirm this for me.