Simple ospf clarification

cnfuzzd

I was taking the practice test here, i encountered this question:

10. You are configuring OSPF on a router with three interfaces with the IP addresses listed below. Which of the following network commands would include all three interfaces in the OSPF routing process in a single area? (Choose all that apply)

Ethernet0 - 192.168.1.2 255.255.255.0
Ethernet - 192.168.2.2 255.255.255.0
Serial1 - 172.16.3.2 255.255.255.252

a. network 0.0.0.0 255.255.255.255 area 0
b. network 192.168.0.0 0.0.255.255 area 0
c. network 255.255.255.255 0.0.0.0 area 0
d. network 192.168.1.2 0.0.0.0 area 0
network 192.168.2.2 0.0.0.0 area 0
network 172.16.3.2 0.0.0.0 area 0

Answer(s): a. network 0.0.0.0 255.255.255.255 area 0
d. network 192.168.1.2 0.0.0.0 area 0
network 192.168.2.2 0.0.0.0 area 0
network 172.16.3.2 0.0.0.0 area 0
Your Answer(s):

a. network 0.0.0.0 255.255.255.255 area 0

Explanation:
The correct command sequence for configuring OSPF in a single area configuration is:
router ospf <process-id>
network <network address> <wildcard mask> area <area number>
Answer A would include all interfaces on the router, the commands in answer D define them individually per interface.

I am just needing some clarification. I am in a way of thinking that says the last three commands listed above would not add the networks because they use the specific address of the interface instead of just the actual network portion of the address. Im also thinking if you wanted to do use it by interface, you could use a "network 192.168.2.2 0.0.0.255" command?

Thanks for the help.

peace

john nickle

Netstudent

Answer A means match everything.

D means match exactly because of the wildcard mask 0.0.0.0


You are activating OSPF on those interfaces that have those addresses. You aren;t necesarily activating "networks" to be advertised but rather the interfaces that will advertise routing updates.

network 192.168.2.2 0.0.0.255 is not a a network.

You would need 192.168.2.0 0.0.0.255 area 0

but this would only cover the interfaces with 192.168.2.0 and not the other inetrfaces in the question.