Cisco CCNA mock exam questions sample test – Question 240

You instructed your assistant to add a new router to the network. The routers in your network run OSPF. The existing router, OldRouter, is configured as follows:
router ospf 1
network 192.168.5.0 0.0.0.255 area 0
network 192.168.10.0 0.0.0.255 area 0
The OldRouter interface that connects to NewRouter is 192.168.5.3/24. Your assistant shows you the configuration that will be implemented:
newrouter(config)# router ospf 1
newrouter(config-router)# network 192.168.5.0 255.255.255.0 area 0
What is wrong with this configuration?

A. The area ID is incorrectly configured.
B. The wildcard mask is incorrectly configured.
C. The network statement is incorrectly configured.
D. The process ID number is incorrectly configured.

Correct Answer: B

Explanation:
When entering network statements for OSPF, a wildcard mask is used instead of a regular mask. Since the network connecting the two routers is a class C network, as shown by the
address 192.168.5.0/24, the wildcard mask should be 0.0.0.255 rather than 255.255.255.0. With wildcard masks, the 0s octets must match, and the 255s octets do not have to match.
The area ID is correct. OldRouter is in area 0, so NewRouter should be as well. There must be an area 0 in an OSPF network. There can be multiple areas as well, but they must all
connect to area 0. If non-0 areas cannot be directly connected to area 0, they must be configured with a virtual link across an area that does connect to the backbone (area 0).
The network statement is correct. The network between the routers is 192.168.5.0.
The process ID number is correct. The number is stated as OSPF 1 on OldRouter and OSPF 1 on NewRouter. They match in this case but that is not required. Process IDs are only
locally significant.
Objective:
Routing Fundamentals
Sub-Objective:
Configure, verify, and troubleshoot single area and multi-area OSPFv2 for IPv4 (excluding authentication, filtering, manual summarization, redistribution, stub, virtual-link, and LSAs)
References:
Internetworking Technology Handbook > Open Shortest Path First (OSPF)