IP ConnectivityDifficulty 3/5
Two routers on the same link show OSPF neighbor state stuck in EXSTART. Which problem is the most likely cause?
- AMismatched hello timers
- BMTU mismatch between the interfaces
- CDifferent area IDs
- DOne interface is passive
Show answer and rationale
Correct: B. EXSTART/EXCHANGE negotiate database description packets; an MTU mismatch prevents the exchange from completing, so neighbors stall in EXSTART. Hello/area mismatches prevent reaching 2-WAY at all, and a passive interface sends no hellos.
- A — Hello/dead mismatches stop adjacency before INIT/2-WAY.
- C — Area mismatch prevents hello acceptance entirely.
- D — A passive interface never forms a neighbor relationship.