Cisco CCNA Single-Area OSPFv2 Configuration 2 — Questions and Answers
Question 1: A router is configured with 'router ospf 1' and 'network 10.1.1.0 0.0.0.255 area 0'. What does the wildcard mask 0.0.0.255 specify?
- Only the exact host 10.1.1.0 participates in OSPF
- Any interface with an IP in the 10.1.1.0/24 range participates in OSPF (Correct answer)
- All interfaces on the router participate in OSPF area 0
- Only interfaces with subnet mask 255.255.255.0 participate
Correct answer: Any interface with an IP in the 10.1.1.0/24 range participates in OSPF
The wildcard mask 0.0.0.255 matches any IP address in the 10.1.1.0/24 range, enabling OSPF on those interfaces.
Question 2: Which OSPF packet type is used to discover and maintain neighbor relationships?
- DBD (Database Description)
- LSR (Link State Request)
- Hello (Correct answer)
- LSU (Link State Update)
Correct answer: Hello
Hello packets are sent periodically to discover neighbors and maintain adjacencies by confirming the neighbor is still reachable.
Question 3: What is the default OSPF Hello interval on a broadcast multi-access network?
- 10 seconds (Correct answer)
- 30 seconds
- 40 seconds
- 60 seconds
Correct answer: 10 seconds
The default Hello interval on broadcast multi-access networks (like Ethernet) is 10 seconds.
Question 4: A network administrator uses 'ip ospf 1 area 0' on an interface instead of the 'network' command. What is the result?
- The command is invalid and will be rejected
- Only that specific interface is enabled for OSPF area 0 (Correct answer)
- All interfaces on the router join area 0
- The router becomes an OSPF DR for area 0
Correct answer: Only that specific interface is enabled for OSPF area 0
The interface-level 'ip ospf process-id area area-id' command enables OSPF directly on that specific interface.
Question 5: What happens when two OSPF neighbors have mismatched Hello intervals?
- OSPF adjacency still forms but with reduced performance
- The neighbor with the higher interval adjusts to match
- The routers will not form an OSPF adjacency (Correct answer)
- OSPF uses the average of both intervals
Correct answer: The routers will not form an OSPF adjacency
OSPF requires Hello and Dead intervals to match between neighbors; mismatched timers prevent adjacency formation.
Question 6: An OSPFv2 router has the following loopback interfaces: Lo0 = 1.1.1.1/32, Lo1 = 2.2.2.2/32. No manual router-id is configured. What is the router ID?
- 1.1.1.1
- 2.2.2.2 (Correct answer)
- The lowest active physical interface IP
- The highest active physical interface IP
Correct answer: 2.2.2.2
When no manual router ID is set, OSPF selects the highest IP address among all loopback interfaces.
Question 7: Which command verifies that OSPF is advertising the correct networks to neighbors?
- show ip ospf neighbor
- show ip ospf database (Correct answer)
- show ip route ospf
- show ip ospf interface
Correct answer: show ip ospf database
The 'show ip ospf database' command displays the LSDB contents, showing which networks are being advertised via LSAs.
Cisco CCNA Single-Area OSPFv2 Configuration 2
A router is configured with 'router ospf 1' and 'network 10.1.1.0 0.0.0.255 area 0'.
What does the wildcard mask 0.0.0.255 specify?