Cisco Certified Support Technician (CCST) NetworkingIP ConnectivityMedium
A network engineer is configuring a router to use OSPF (Open Shortest Path First) as its interior gateway protocol. The engineer wants to ensure that all interfaces participating in OSPF are included in Area 0. Which of the following OSPF commands, when configured under router OSPF 1, will enable OSPF on the interface with IP address 192.168.10.1/24 and assign it to Area 0?
- Anetwork 192.168.10.0 0.0.0.255 area 1
- Bip ospf 1 area 0 on GigabitEthernet0/1
- Cnetwork 192.168.10.0 0.0.0.255 area 0
- Dinterface GigabitEthernet0/1 ip ospf 1 area 0
Show answer & explanationAnswer & explanation
Correct answer: C. network 192.168.10.0 0.0.0.255 area 0
In Cisco IOS for OSPF, the `network` command under the `router ospf` configuration mode is used to specify which interfaces belong to an OSPF area. The command `network 192.168.10.0 0.0.0.255 area 0` matches any interface whose IP address falls within the 192.168.10.0/24 range and places it into OSPF Area 0.
Why the other options are wrong
- A. This command places the network into Area 1, not Area 0, and uses the correct wildcard mask.
- B. This command has incorrect syntax for configuring OSPF under `router ospf` mode or on an interface.
- D. This is an interface-specific command, but the syntax `ip ospf <process-id> area <area-id>` is configured directly on the interface, not under `router ospf` mode, and it's missing the `network` statement.
OSPF Network Command
The `network` command in OSPF configuration globally enables OSPF on interfaces whose IP addresses fall within the specified range and assigns them to a particular OSPF area.
- Uses a wildcard mask (inverse of subnet mask) to define the range.
- Activates OSPF on matching interfaces.
- Assigns interfaces to a specific OSPF area.
Memory trick: To plug an interface into OSPF, you declare its network and its area.