A 911 PSAP reports an OSPF adjacency that never reaches FULL between two routers on a shared Ethernet segment. Timers show mismatched hello and dead intervals. What should the engineer conclude?
Select an answer to reveal the explanation.
Short Explanation
OSPF neighbors have to agree on how often they say hello and when silence means dead — like two dispatchers on the same radio cadence. Mismatched hello/dead timers keep the adjacency from forming. EtherChannel, HSRP myths, and PC VNIs aren't the cause.
Full Explanation
At the 911 PSAP, an OSPF adjacency stuck short of FULL with mismatched hello and dead intervals should lead the engineer to conclude that hello/dead timer mismatches prevent OSPF neighbor adjacency formation. OSPF neighbors on a common network type must agree on hello and dead timers (among other parameters); mismatch keeps the adjacency from progressing through the expected states to FULL, so LSDB exchange never completes on that segment.
Claiming timer mismatches only affect EtherChannel hashing denies OSPF's actual dependency on matching hello/dead values for adjacency. Saying OSPF ignores hello timers whenever HSRP exists anywhere in the city is false—HSRP and OSPF timers are independent control planes. Blaming missing VXLAN VNIs on PSAP PCs invents a data-center overlay dependency unrelated to classic OSPF timer mismatch on a shared Ethernet segment.
Exam caveat: other adjacency blockers include area ID mismatch, authentication mismatch, stub flags, MTU issues, and network-type mismatches—but this stem specifically points to hello/dead timers. Dead interval is typically four times hello by default; manual changes must be mirrored on both neighbors. ENCOR expects you to treat timer mismatch as a hard adjacency failure cause, not a cosmetic warning.
Operational check: on both PSAP routers, compare show ip ospf interface hello/dead values on the shared segment, align them, and clear/restart the neighbor to confirm FULL state and LSDB sync. Verify 911 prefixes appear correctly after adjacency recovers. Standardize timer templates for civic OSPF Ethernet segments so future closet swaps do not reintroduce silent mismatches.