Cisco CCNA Single-Area OSPFv2 Configuration 4 — Questions and Answers
Question 1: After configuring OSPFv2, a router shows neighbor state as '2-Way' rather than 'Full'. What does this indicate?
- The neighbor relationship is fully established and working normally
- Both routers see each other's Hellos but are not DR/BDR, which is normal for DROTHER routers (Correct answer)
- There is an authentication mismatch preventing full adjacency
- The routers have mismatched OSPF area IDs
Correct answer: Both routers see each other's Hellos but are not DR/BDR, which is normal for DROTHER routers
2-Way state is normal between two DROTHER routers on a multi-access segment; Full adjacency only forms with the DR and BDR.
Question 2: What is the multicast address used by OSPFv2 to send Hello packets to all OSPF routers?
- 224.0.0.5 (Correct answer)
- 224.0.0.6
- 224.0.0.9
- 255.255.255.255
Correct answer: 224.0.0.5
OSPFv2 uses 224.0.0.5 (AllSPFRouters) to send Hello packets and LSAs to all OSPF-enabled routers.
Question 3: A router's OSPF neighbor table shows a neighbor stuck in the 'EXSTART' state. What is the most likely cause?
- Duplicate OSPF router IDs on the network (Correct answer)
- Mismatched Hello intervals
- The neighbor's interface is passive
- Mismatched OSPF process IDs
Correct answer: Duplicate OSPF router IDs on the network
Duplicate router IDs cause OSPF to get stuck in ExStart because routers cannot agree on master/slave roles during DBD exchange.
Question 4: Which command manually sets the OSPF cost on an interface to 50?
- router ospf 1 → cost 50
- ip ospf cost 50 (interface mode) (Correct answer)
- bandwidth 50 (interface mode)
- ip ospf priority 50 (interface mode)
Correct answer: ip ospf cost 50 (interface mode)
The 'ip ospf cost value' command in interface configuration mode directly sets the OSPF cost for that interface.
Question 5: How does OSPFv2 handle equal-cost paths to the same destination by default on Cisco routers?
- Only the path with the lowest router ID is used
- Traffic is load-balanced across up to 4 equal-cost paths (Correct answer)
- The most recently learned path is preferred
- Only one path is installed; the other is held as a backup
Correct answer: Traffic is load-balanced across up to 4 equal-cost paths
Cisco routers perform equal-cost load balancing (ECMP) across up to 4 paths by default when OSPF finds multiple equal-cost routes.
Question 6: What is the effect of configuring 'ip ospf priority 0' on a router interface?
- The router becomes the DR for that segment
- The router is ineligible to become DR or BDR on that segment (Correct answer)
- The router's OSPF cost is set to zero
- OSPF is disabled on that interface
Correct answer: The router is ineligible to become DR or BDR on that segment
An OSPF priority of 0 makes the router ineligible for DR/BDR election on that network segment.
Question 7: A technician clears the OSPF process with 'clear ip ospf process'. What immediately happens?
- OSPF is permanently disabled until re-enabled
- All OSPF neighbor adjacencies are torn down and re-established from scratch (Correct answer)
- Only the routing table is cleared; adjacencies remain
- The OSPF process ID is reset to 1
Correct answer: All OSPF neighbor adjacencies are torn down and re-established from scratch
Clearing the OSPF process drops all adjacencies and triggers a full re-convergence including neighbor discovery and LSDB exchange.
Cisco CCNA Single-Area OSPFv2 Configuration 4
After configuring OSPFv2, a router shows neighbor state as '2-Way' rather than 'Full'.
What does this indicate?