Finding out the Network ID

[timmspfc13]

I am kind of stuck on this problem here identifying the Network ID of this address: 13.1.255.102.

I know that the subnet mask + host ID = Network ID, but I'm having trouble getting started. If it was 13.1.255.102/24 I could easily find it. How do I find out the network ID?

[Charles Hill]

You need to know the subnet before you can determine the network id.

If it is a classful network, the network id is 13.0.0.0, since class A address range is

10.0.0.0 - 10.255.255.255.