Checking Current Timers
R1# show ip ospf interface gi0/0 | include Timer
Timer intervals configured, Hello 10, Dead 40
Changing Timers
Per-Interface Configuration
interface gi0/0
ip ospf hello-interval 5
ip ospf dead-interval 20
Must match on both sides of link!
Timer Mismatch Troubleshooting
Symptom
R1# show ip ospf neighbor
(No neighbors)
Debug
R1# debug ip ospf adj
*OSPF-1 ADJ: Mismatched hello parameters from 10.1.1.2
*OSPF-1 ADJ: Dead R 40 C 20, Hello R 10 C 5
R = Received, C = Configured
Fix
Match timers on both routers:
R2(config-if)# ip ospf hello-interval 10
R2(config-if)# ip ospf dead-interval 40
When to Tune Timers
Faster Convergence
Lower timers = faster failure detection
ip ospf hello-interval 1
ip ospf dead-interval 4
Caution: Increases CPU/bandwidth usage
Slower Networks
Increase timers on high-latency links
ip ospf hello-interval 30
ip ospf dead-interval 120
Summary
✅ Hello timer — How often to send Hellos
✅ Dead timer — When to declare neighbor dead
✅ Must match — Both routers need same timers
✅ Tune carefully — Balance convergence vs overhead
Next: Learn about OSPF Network Types (Article 17)
Internal Links:
- ← OSPF Virtual Links (Article 15)
- ← OSPF Neighbor States (Article 3)
- → OSPF Network Types (Article 17)
- → Neighbors Not Forming (Article 18)
