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IPv6 Subnet Calculator

Calculate an IPv6 subnet from an address and prefix length: network address, first and last address, total addresses, and full notation.

About IPv6 Subnet Calculator

An IPv6 address is 128 bits long, written as eight groups of four hexadecimal digits, and a prefix length such as /64 says how many leading bits identify the network. This calculator clears the remaining bits to get the network address, sets them to get the last address, and counts 2 to the power of (128 minus prefix) addresses. It shows both the compressed form defined in RFC 5952 and the fully expanded form.

How to use IPv6 Subnet Calculator

  1. Fill in "IPv6 address" and "Prefix length".
  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 IPv6 Subnet Calculator

Why is /64 the standard IPv6 subnet size?

Stateless address autoconfiguration (SLAAC) builds the last 64 bits of an address from the interface, so it needs a 64-bit network part. A /64 holds about 18.4 quintillion addresses, and using it everywhere keeps addressing plans simple.

Runs in your browser. Page last updated .

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