Subnet Mask To Wildcard Mask

What is a Wildcard Mask?

Wildcard Mask is a 32 bit number similar to a Subnet Mask, a wildcard mask is also used in subnetting to identify a group of IP addresses. Although wildcard mask and subnet mask are similar, A wildcard mask does not specify which portion of the IP address is the host and network portions. A wildcard mask does specify which portion of the IP address should be ignored (masked out) when performing a routing operation.

Wildcard masks are used primarily in access control rules and routing. The access control rules contain the match a specific pattern or a range of IP addresses. Wildcard masks are used alongside Subnet masks to give a more agility and powerful method of outline and matching groups of IP addresses on a network.

In Binary notation, the structure of a Wildcard Mask consists of a series of zeros followed by a series of ones. Usually the Wildcard Mask is the inverse of the Subnet Mask. In a Wildcard mask the zeros represent the bits that should be matched, where the ones represent the bits that should be ignored. For example a Wildcard Mask 0.255.255.255 would comprise 24 zeros and 8 ones. The first eight bits of the octet are matched where the remaining 24 zeros would be ignored.