Handitab

Subnet Cheat Sheet

Look up every IPv4 prefix length from /0 to /32 with its subnet mask, wildcard mask, total addresses, and usable host count.

About Subnet Cheat Sheet

A subnet cheat sheet lists each CIDR prefix length with its dotted-decimal subnet mask. A prefix of /n means the first n of 32 bits identify the network, which leaves 2 to the power of (32 minus n) addresses. Two of those, the network and broadcast addresses, cannot be given to hosts, so usable hosts are the total minus 2. The exceptions are /31, used for point-to-point links under RFC 3021, and /32, a single host.

How to use Subnet Cheat Sheet

  1. Fill in "Show from prefix" and "Show to prefix".
  2. The result appears below and updates as you type.
  3. Copy the result with the copy button, or download it as a file where that is offered.

Questions about Subnet Cheat Sheet

What is a wildcard mask?

A wildcard mask is the bitwise inverse of a subnet mask: 0.0.0.255 for 255.255.255.0. Access control lists and OSPF on Cisco devices use it to mark which address bits may vary.

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