Convert between subnet masks and wildcard masks for Cisco ACLs.
-
-
-
access-list or network statement.A wildcard mask is the bitwise inverse of a subnet mask. Where a subnet mask uses 1s to mark network bits, the wildcard uses 0s to mark bits that must match.
Wildcard masks let an ACL match non-contiguous bit patterns, which subnet masks cannot represent. In practice most ACLs use contiguous wildcards equivalent to a CIDR prefix.
Yes. A wildcard like 0.0.255.255 matches any second-half octet, but 0.0.0.85 matches only odd third-octet values — useful for advanced filtering tricks.
0.0.0.0 — every bit must match exactly. Cisco IOS also accepts the keyword host as a shorthand.