Free tool · IP & Subnetting
Wildcard Mask Calculator
Convert subnet masks to wildcard masks for ACLs and OSPF.
Binary
Mask11111111.11111111.11111111.00000000
Wildcard00000000.00000000.00000000.11111111
Example ACL line: access-list 10 permit 10.0.0.0 0.0.0.255
About this tool
Free wildcard mask calculator. Convert a subnet mask or CIDR prefix to the inverse (wildcard) mask used in Cisco ACLs and OSPF network statements, and back again — with binary view. Everything runs entirely in your browser — nothing you type is sent to a server.
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