A range of 2n addresses, where n is 0, 1, 2, 3...
For the first address of the range, modulus 2n must be zero.
This also causes the last address of the range modulus 2n to be
2n-1.
IP block
A block of IP addresses, or in other words, the range of addresses
given in the CIDR notation specified by RFC 1519.
IPv4 block
A range of 2n IP addresses, where n is in N and [0,31],
and the first address of the range modulus 2n is 0.