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Network

Wildcard Mask Calculator

Convert subnet masks into wildcard masks for ACL rules.

Wildcard Mask Calculator converts subnet masks to wildcard masks for ACL and network policy use. It is useful in environments where control lists require wildcard notation rather than CIDR. The tool prevents common inverse-mask mistakes. Use it when preparing router and firewall access rules.

Wildcard Mask Input

Result

Wildcard mask: 0.0.0.255

Mask bits: 11111111.11111111.11111111.00000000

Wildcard bits: 00000000.00000000.00000000.11111111

How to use this tool

  1. Enter subnet mask or CIDR prefix.
  2. Run conversion to generate wildcard mask output.
  3. Apply result in ACL entries and validate against test traffic.

Firewall and ACL resources

Promote network security tools, ACL references, and certification labs.

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