CIDR to Subnet and Wildcard Mask
CIDR notation describes how many leading bits identify the network. A /24 uses 24 network bits. The subnet mask represents those bits as ones, while the wildcard mask inverts them.
Network and Host Range
The network address is obtained by applying the subnet mask to the IPv4 address. The broadcast address sets all host bits to one. Conventional subnets from /0 through /30 reserve the network and broadcast addresses.
Cisco Wildcard Masks
Wildcard masks are commonly used in Cisco access-control and routing configurations. For example, 192.168.1.0/24 corresponds to network 192.168.1.0 with wildcard mask 0.0.0.255.
Frequently Asked Questions
What is a wildcard mask?
A wildcard mask is the inverse of a subnet mask. Cisco-style ACL configurations commonly use wildcard masks to identify which address bits must match.
What is the wildcard mask for /24?
A /24 subnet mask is 255.255.255.0, so the corresponding wildcard mask is 0.0.0.255.
How many usable hosts are in a /27?
A conventional IPv4 /27 contains 32 total addresses and normally provides 30 usable host addresses.
Does the calculator support /31 networks?
Yes. It treats a /31 as a two-address point-to-point network rather than subtracting network and broadcast addresses.