What Does Wildcard Mask Mean in 200-301?
Also known as: inverse mask
Quick Definition
The inverse of a subnet mask, used in ACLs and OSPF network statements.
Full Definition
A wildcard mask is the bitwise inverse of a subnet mask. Where the subnet mask has 1s in the network portion, the wildcard mask has 0s (meaning 'must match'). Where the subnet mask has 0s in the host portion, the wildcard mask has 1s (meaning 'don't care'). Wildcard masks appear in ACLs and in OSPF network statements. A wildcard mask of 0.0.0.255 matches any host in a /24 subnet.
Real-World Example
To permit all hosts in 192.168.1.0/24: access-list 1 permit 192.168.1.0 0.0.0.255. The wildcard 0.0.0.255 means the first three octets must match exactly, but the last octet can be anything.
Exam Trap — Don't Get Fooled
Wildcard masks are NOT subnet masks. 0.0.0.255 is the wildcard for a /24, but it is NOT the subnet mask (which would be 255.255.255.0). Confusing the two is one of the most common CCNA mistakes.
Related 200-301 Terms
Frequently Asked Questions
What does Wildcard Mask mean on the 200-301 exam?
A wildcard mask is the bitwise inverse of a subnet mask. Where the subnet mask has 1s in the network portion, the wildcard mask has 0s (meaning 'must match'). Where the subnet mask has 0s in the host portion, the wildcard mask has 1s (meaning 'don't care'). Wildcard masks appear in ACLs and in OSPF network statements. A wildcard mask of 0.0.0.255 matches any host in a /24 subnet.
How does Wildcard Mask appear as a trap on the 200-301?
Wildcard masks are NOT subnet masks. 0.0.0.255 is the wildcard for a /24, but it is NOT the subnet mask (which would be 255.255.255.0). Confusing the two is one of the most common CCNA mistakes.
Can you give a real-world example of Wildcard Mask?
To permit all hosts in 192.168.1.0/24: access-list 1 permit 192.168.1.0 0.0.0.255. The wildcard 0.0.0.255 means the first three octets must match exactly, but the last octet can be anything.
How important is Wildcard Mask on the 200-301 exam?
Wildcard Mask falls under the IP Addressing domain of the 200-301 exam. Understanding it in context with related terms like acl and subnet-mask is essential for answering scenario-based questions correctly.