IP Address inquiry

[pjcod47]

Hello, my home network's IP address is 10.1.1.25. I'm just curious as to why my subnet mask is 255.255.255.0. Since I have class A, it should be 255.0.0.0, right?

[Flavio Miranda · Accepted solution]

Hi @pjcod47 

 It would be true in the past but then it was developed the concept of VLSM (variable length subnet mask)

 So,  you are able now to use any subnet with any mask. Now a days pratically all devices support vlsm.

[Joseph W. Doherty]

Actually, before there was CIDR or VLSM a classful network could be, and for a Class A or B address block could be, and likely was, subnetted.

That aside, how a host uses its network mask doesn't need to always directly correspond to how routers route network prefixes.  For example, do you understand the significance of a network mask to a host?  Again, it's not the same as it is to a router.

So, to OP's "should it be" question, the answer is probably not, even under Classful rules and/or FLSM, because it's a host.

[Nbell2015]

10.0.0.0 - 10.255.255.255 is a private network address range and does travel across the internet, so the subnet mask can be A, B, or C. It wont' matter. What will matter is that every in the LAN uses the same subnet mask, or they won't communicate.

Hope this helps

Nav

[Joseph W. Doherty]

Believe you may have intended to write private networks do NOT travel across the Internet.

As to hosts needing same network mask, well that's the norm, but exceptions can exist based on whether "communication" is one or two way and whether host has a gateway defined.