Something wrong with my understanding in subnettin

Question

I did "ipconfig" at my computer, and its gave me this thing:

IPv4 Address. . . . . . . . . . . : 10.100.102.8

Subnet Mask . .. . . . . . . . . : 255.255.255.0

Is any reason in here? from what I learned - if "10" in the first octet, thats means this ip is class A. But in the subnet mask the "ipconfig" gave me, its like the "10" pointing to class C. If someone can explain me this.

Answer 1

10.x.x.x is just something that can be reused locally-- it's not routable. Call it "class A" if you want, but that terminology is confusing in this context.

The mask is what splits the network from the hosts. When you have networks under networks, you have sub-networks, or subnets. The subnet mask (often called simply "mask") is what tells you what part of an address is network and what part isn't.

This example doesn't even require going to binary (and the class-A,B,C terminology is only confusing here): 10.100.102.x is your network and 8 is your host.

Listen to and obey the subnet mask.