Wildcard mask question on CCNA

damian86

Distinguished
May 17, 2009
683
0
19,010
Hi,

I am reviewing my answers and I managed to get this one right but I do not understand it. Wildcard masks are a little bit confusing.

It says: OSPF has been configured with the following command: network 192.168.1.32 0.0.0.31 area 0

Which router interface will participate in OSPF?

The right answer is Serial S0/0/0 192.168.1.35. But why, how do we work this out?

Thanks!
 

Simo606

Honorable
May 11, 2012
292
0
10,860
The wildcard mask is the inverse of a subnet mask. So the wild mask of 0.0.0.31 equals a subnet mask of 255.255.255.224. This subnet is large enough for 32 addresses.

So with that wildcard mask the address range is 192.68.1.32 to 192.168.1.63, which are advertised into OSPF. Since 192.168.1.35 falls within that range, it will participate in OSPF.