ICND1 OSPF Configuration 3 — Questions and Answers
Question 1: What is the default OSPF dead interval on a broadcast network?
- 10 seconds
- 30 seconds
- 40 seconds (Correct answer)
- 60 seconds
Correct answer: 40 seconds
The default dead interval is 40 seconds, which is 4 times the default hello interval of 10 seconds.
Question 2: Which command configures a passive interface in OSPF, preventing hello packets from being sent out that interface?
- ip ospf passive
- passive-interface GigabitEthernet0/0 (Correct answer)
- no ip ospf hello
- ip ospf network passive
Correct answer: passive-interface GigabitEthernet0/0
The 'passive-interface' command under the OSPF process stops hellos on that interface while still advertising the connected network.
Question 3: Which OSPF LSA type describes a router's directly connected links within an area?
- Type 2 (Network LSA)
- Type 3 (Summary LSA)
- Type 1 (Router LSA) (Correct answer)
- Type 5 (AS External LSA)
Correct answer: Type 1 (Router LSA)
Type 1 Router LSAs are generated by every OSPF router and describe that router's links within the area.
Question 4: What is the purpose of the 'area 0' designation in OSPF?
- It is a stub area that blocks external routes
- It is the backbone area that all other areas must connect to (Correct answer)
- It is a reserved area for loopback interfaces
- It limits OSPF to a single router
Correct answer: It is the backbone area that all other areas must connect to
Area 0 is the OSPF backbone area, and all other areas must connect to it either directly or via a virtual link.
Question 5: A router running OSPF has a cost of 10 on Fa0/0 and 100 on Fa0/1. Which path will OSPF prefer to reach a remote network?
- Fa0/1 because higher cost means faster link
- Fa0/0 because OSPF prefers lower cost (Correct answer)
- Both paths are used via load balancing by default
- Fa0/1 because higher bandwidth is preferred
Correct answer: Fa0/0 because OSPF prefers lower cost
OSPF uses the lowest cumulative cost path, so the interface with cost 10 is preferred over cost 100.
Question 6: Which command displays the OSPF neighbor table on a Cisco router?
- show ip route ospf
- show ip ospf database
- show ip ospf neighbor (Correct answer)
- show ip ospf interface
Correct answer: show ip ospf neighbor
'show ip ospf neighbor' displays the neighbor ID, state, dead time, and interface for each OSPF neighbor.
Question 7: What does it mean when a neighbor shows 'FULL/DR' in the 'show ip ospf neighbor' output?
- The neighbor is fully adjacent and is the Designated Router (Correct answer)
- The neighbor's LSDB is full and it acts as DR
- The adjacency failed and the router is the DR
- The neighbor is a fully meshed DR-only router
Correct answer: The neighbor is fully adjacent and is the Designated Router
FULL/DR means the router has reached full adjacency with that neighbor, which is the Designated Router on the segment.
ICND1 OSPF Configuration 3
What is the default OSPF dead interval on a broadcast network?