Die Antwort musste vor Jahren mal so lauten, heute jedoch nicht mehr:
The all-zeros and all-ones subnets
RFC 950 originally forbade the use of the subnetted network IDs where the bits being used for subnetting are set to all 0s (the all-zeros subnet) and all 1s (the all-ones subnet). The all-zeros subnet caused problems for early routing protocols and the all-ones subnet conflicts with a special broadcast address called the all-subnets directed broadcast address.
However, RFC 1812 now permits the use of the all-zeros and all-ones subnets in a Classless Interdomain Routing (CIDR)-compliant environment. CIDR-compliant environments use modern routing protocols which do not have a problem with the all-zeros subnet and the use of the all-subnets directed broadcast has been deprecated.
Before you use the all-zeros and all-ones subnets, verify that they are supported by your hosts and routers. Windows NT supports the use of the all-zeros and all-ones subnets.