A router has been configured with the commands router ospf 9, network 172.16.1.0
0.0.0.255 area 8, and network 172.16.0.0 0.0.255.255 area 9, in that order. No other OSPFrelated commands have been configured. The answers list the IP addresses that could be
assigned to this router’s Fa0/0 interface. Which answers list an IP address/prefix length that
would cause the router to put Fa0/0 into area 9? (Choose two.)
A.
172.16.0.1/23
B.
172.16.1.1/26
C.
172.16.1.1/24
D.
172.16.0.255/23
E.
None of the other answers is correct.
Explanation:
The wildcard mask is used for matching the prefix only, and not the prefix
lengtH. As such, 172.16.1.0 0.0.0.255 matches all addresses that begin with 172.16.1,
and 172.16.0.0 0.0.255.255 matches all addresses that begin 172.16. Also, OSPF reviews
the network command with the most specific wildcard masks (wildcard masks
with the most binary 0’s) first, so an interface IP address beginning with 172.16.1
matches the command that references area 8.