Block Sizes

[Fuzz]

A block size is always a power of 2, so they are 1, 2, 4, 8, 16, 32, 64, 128 and 256. Blocks of 1 and 256 take care of themselves, so just learn the others.

48 is not a block size, it is a multiple of 16, 8, 4 and 2. This is important beacuse a subnet address must start with a multiple of it's block size. In other words, a subnet of block size 32 cannot begin on 48, only 0, 32, 64 etc.

Originally Posted by Ltat42a

If your subnet mask is 255.255.255.128 (subnetting in 4th octet), your block size (or network range) is 2. One network is 0-127, the other is 128 -255

Here, the block size is 128. Block size is always 256 - mask in the interesting octet.