ip subnet-zero — global
ip subnet-zero no ip subnet-zero
The zero subnet
Enabled in recent versions of IOS (12.X)
When subnetting a network, the 0 subnet (the subnet whose subnet bits are all 0) is normally not allowed because of potential confusion between the subnet address and the network address. In practice, this confusion is rarely an issue. This command allows the router to use the all-zeros subnet.
The following command enables the zero subnet: