YurlieWildcard Mask Calculator
Convert between subnet masks and wildcard masks. Wildcard masks are the bitwise inverse of subnet masks, used in Cisco ACLs and OSPF.
Subnet mask
255.255.255.0/24⇄
Wildcard mask
0.0.0.2550x000000FFBinary
Mask
11111111111111111111111100000000
Wildcard
00000000000000000000000011111111
Prefix
/24Total IPs
256Usable hosts
254Mask hex
0xFFFFFF00Common mask reference
PrefixSubnet maskWildcardHosts
Wildcard Masks in Cisco ACLs
A wildcard mask is the bitwise complement of a subnet mask. A 0 bit means "must match", a 1 bit means "any value is OK". For example, wildcard 0.0.0.255 matches any host in the /24 subnet.