what is subnet mask width?

Answer 1

xxx.xxx.xxx.xxx Same as an IP address
Four number between 000 and 255 separated by commas

What a subnet mask does is tell a router how much of the IP address is the network's address and how much is the individual PC's address.

Say you have the IP address 192.168.001.100. If the network is address 192.168.001, then the computer is computer number 100. You would use the subnet mask 255.255.255.0 Everything that is 255 in the mask is part of the network address. Everything that is 0 in the mask is the PC address. If the mask was 255.255.0.0, then the network address would be 192.160, and the computer number 000.100. If the mask is 255.0.0.0, then the network address is 192 and the computer is computer number 168.001.100.

If is possible to make a subnet mask with numbers other than 255 and 0. That mask would allow you to access only small segments of a larger network, and involve binary math to determine the subnet mask numbers. But they are not common.

The standard configuration for a home network is to have the network address be 192.168.0, the router is 192.168.0.1, each computer is number beginning at 192.168.0.100, and the subnet mask is 255.255.255.0

Answer 2

in IPV4, it's 4 bytes.