Determining if two IP adresses are on same subnet - is it leading or trailing 0s get dropped from IP address?

Question

I understand if two IP addresses are AND\'d with a subnet mask if the result is the same then they are on the same network. If the result is different then they are on diffe

Answer 1

You are completely missing something: You don't just concat your digits together, because AND works on binary level.

So either you process the IPv4 addresses byte-wise, or you transform them into a decimal number, but not with factor 1000, but with factor 256.

This is to say, instead of doing

((126 * 1000 + 1) * 1000 + 0) * 1000 + 10 = 126001000010

you should do

((126 * 256 + 1) * 256 + 0) * 256 + 10 = 2113994762

. If you apply this to the other numbers, you should succeed.

Alternatively, you could AND together the 4 numbers separately, so

255 & 126 = 126 (in both cases), 128 & (1 resp. 127) = 0, 0 & (anything) = 0, 0 & (anything) = 0.

So you get 126.0.0.0 for both, making them belong to the same subnet.