Detection
Check Authentication Type
R1# show ip ospf interface gi0/0 | include auth
Message digest authentication enabled
R2# show ip ospf interface gi0/0 | include auth
Simple password authentication enabled ← MISMATCH!
Debug Output
R1# debug ip ospf adj
*OSPF-1 ADJ: Mismatch Authentication type. Input packet specified type 1, we use type 2
Fix: Match Authentication Type
Both routers use MD5:
R2(config)# interface gi0/0
R2(config-if)# ip ospf authentication message-digest
R2(config-if)# ip ospf message-digest-key 1 md5 SecurePassword
Fix: Match Passwords
Check configured password (hidden):
R1# show run interface gi0/0 | include key
ip ospf message-digest-key 1 md5 7 060506324F41
Set matching password on R2:
R2(config-if)# ip ospf message-digest-key 1 md5 SecurePassword
Summary
✅ Match auth type — Both plain text or both MD5
✅ Match passwords — Exact same password
✅ Match key IDs — Same key ID number
Next: Routes Not Appearing (Article 23)
Internal Links:
- ← Area Mismatch (Article 19)
- ← OSPF Authentication (Article 13)
- ← Neighbors Not Forming (Article 18)
