300-410 Question 65

Community Discussion

Written by other learners. Comments can disagree with the marked answer — check the official documentation when in doubt.

• Chose D1

  if there is a mis match in the Timers the Adjacency will not be established.

• Chose B1

  The key is "Nov 29 15.20.27.995: OSPF-1 HELLO Fa0/0: Dead R 40 C 40, Hello R 10 C 10 Mask R 255.255.255.0 C 255.255.255.240" Parameters (R vs C) Dead R 40 C 40 Dead R = The Dead Interval received in the neighbor’s Hello packet = 40 seconds. Dead C = The Dead Interval configured locally on your router for that interface = 40 seconds. ✅ They match, which is required for neighbors to form adjacency. Hello R 10 C 10 Hello R = The Hello Interval received in the neighbor’s Hello packet = 10 seconds. Hello C = The Hello Interval configured locally = 10 seconds. ✅ These also match — another adjacency requirement. Mask R 255.255.255.0 C 255.255.255.240 Mask R = The subnet mask received in the neighbor’s Hello packet = /24. Mask C = The subnet mask configured locally on your interface = /28. ⚠️ Mismatch here! OSPF neighbors must be in the same subnet, and the masks must match on broadcast and NBMA networks (like Ethernet). This mismatch will prevent adjacency.

• 4

  After two routers discover each other by receiving Hellos from the other router, the routers perform the following parameter checks based on the receive Hellos: ■ Must pass the authentication process ■ Must be in the same primary subnet, including the same subnet mask ■ Must be in the same OSPF area ■ Must be of the same area type (regular, stub, not-so-stubby area [NSSA]) ■ Must not have duplicate RIDs ■ OSPF Hello and Dead timers must be equal If any of these items do not match, the two routers simply do not form a neighbor relationship.