When troubleshooting authentication issues, it is presumed the router adjacencies are configured correctly, so when deploying, do this first so the scope of your troubleshooting can be consolidated to authentication mechanisms, and not something like passive interfaces, etc.
Some commands that are helpful in troubleshooting authentication for EIGRP:
- show key chain
- debug eigrp packets
- show ip eigrp neighbors/show ipv6 eigrp neighbors
- show eigrp address-family ipv4 interfaces detail
Note that named EIGRP configuration holds distinct advantages when troubleshooting adjacency issues because all configuration except for the key chain is done within the address-family (and not on a per-interface basis).
Stuck-in-Active: Journal of an IT-Network Administrator 