Consider a subnet identified as follows: 192.168.31.0/26.
using the ip ranges from this subnet, what is the ip network mask used by hosts on the subnet?
use dotted-decimal notation for the answer.
255.255.255.192
255.255.255.224
255.255.255.128
255.255.255.0

255.255.255.192

Explanation:

Given subnet : 192.168.31.0/26

This implies that there are 26 1-bits in the subnet mask. So the subnet mask is:

11111111.11111111.11111111.11000000   (26 1's)

Translating each segment into decimal representation:

11111111 = 2^7 + 2^6+2^5+2^4+2^3+2^2+2^1+2^0

           = 128+64+32+16+8+4+2+1

           = 255

11000000 = 2^7 + 2^6

                 = 128 + 64

                 = 192

So the overall subnet mask is : 255.255.255.192