x.x.x.255 for class C based addresses
x.x.255.255 for class B based addresses and
x.255.255.255 for class A based addresses may be valid, these are disallowed.
For example, assume the Network Address 22.214.171.124 with a netmask of 255.255.252.0, which results in a supernetted class C address range. This means for two addresses to be on the same network, the first two octets must match exactly, the first six bits of the third octet must match (252=11111100) and the last octet does not matter. For this range, 126.96.36.199 is the network address and 188.8.131.52 is the subnet broadcast address. Every IP address between those two are valid. But the addresses below are disallowed because they are subnet broadcast addresses based on the standard class C subnet mask 255.255.255.0:
Article ID: 281579 - Last Review: Jan 7, 2008 - Revision: 1