Cisco IOS Engineering Tool
Wildcard Mask Calculator
Convert subnet masks to inverted wildcard masks and instantly generate ready-to-paste Cisco IOS Access-List (ACL) and OSPF statements.
Wildcard Mask
0.0.0.255
Inverse of 255.255.255.0
Subnet Mask
255.255.255.0
Dotted decimal netmask
Matched Hosts
256 IPs
Total IP span matched by ACL
Cisco Standard Access-List (ACL) Statement:
Cisco OSPF Network Statement:
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Frequently Asked Questions
Clear answers to common questions about subnetting, CIDR notation, and network design.
What is a Cisco Wildcard Mask?
A Wildcard Mask (inverted mask) is used by Cisco IOS router configurations in Access Control Lists (ACLs) and routing protocols like OSPF and EIGRP. A binary
0 means the bit in the IP packet must match exactly, while a binary 1 means the bit is ignored (wildcard/don't care).How do I calculate a wildcard mask from a subnet mask?
Subtract each octet of the subnet mask from 255.255.255.255. For example, for subnet mask
255.255.255.0: 255-255=0, 255-255=0, 255-255=0, 255-0=255. The resulting wildcard mask is 0.0.0.255.