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Wildcard mask

Wildcard mask definition

A wildcard mask is a method network administrators use to help them identify or select specific groups of IP addresses. It's like a customizable filter for IP addresses, where you can decide which parts of the address you want to focus on and which parts can be ignored.

Network administrators need them because in a large network, managing access or routing for individual IP addresses would be incredibly time-consuming and impractical. Wildcard masks allow administrators to group addresses together based on common patterns, making it easier to apply rules or actions to many addresses at once. In essence, wildcard masks are a flexible way to manage and apply network policies to groups of IP addresses, simplifying network configuration and management.

See also: class A IP address, IP address blocking, IP surveillance, IPsec, IPv4, virtual IP address

How wildcard masks work

An IP address consists of four numbers separated by dots (for example,, and each number can be from 0 to 255. A wildcard mask also looks similar, with four numbers separated by dots, but here, the numbers tell the network device which parts of the IP address to ignore (usually represented by a '1') and which parts to pay attention to (usually represented by a '0').

For example, a wildcard mask of applied to an IP address range tells the network router or switch to ignore the last part of the address and focus on the first three numbers. So, it groups all addresses that match the first three numbers, regardless of the fourth number. This can be very useful for specifying a subset of devices within a larger network without having to list every single IP address individually.