Last octet being .10000000 = 128. Block size: 256-128=128. Increment of 128
Borrowing 9 bits in a class B IP results in third octet all being 1, and first bit in fourth octet being 1. Therefore the final subnet mask is: 11111111.11111111.11111111.10000000 or 255.255.255.128 or /25.
Last octet being .10000000 = 128. Block size: 256-128=128. Increment of 128
Borrowing 9 bits in a class B IP results in third octet all being 1, and first bit in fourth octet being 1. Therefore the final subnet mask is: 11111111.11111111.11111111.10000000 or 255.255.255.128 or /25.