Helpnyx
Sign inTalk to us
Menu

IPv6 subnet calculator

Enter an IPv6 address with its prefix. See the block's first and last address, how many /64 networks it holds, the address written in full and in short form, and how the block splits.

Runs in your browser. Nothing you enter or upload is sent to us.

Our IPAM Enterprise portal manages IPv4 address space today. This calculator is a free tool for anyone working with IPv6.

Try:

How to use it

Three steps

  1. Type an address and prefix. For example 2001:db8:abcd:12::5/64. Short forms with :: are fine. If you leave out the prefix, /64 is used.
  2. Read the block. See the first and last address, the total size and how many /64 networks and /56 sites it holds.
  3. Plan the split. Choose a size such as /48, /56 or /64 to list the blocks inside, for customer sites or VLANs.

Questions

Good to know

Why is /64 the usual size for one network?

IPv6 address autoconfiguration (SLAAC) needs a 64-bit interface ID, so a single LAN or VLAN normally gets a /64.

What size should a customer get?

Common practice is a /48 for a business site and a /56 for a home or small business. That leaves room for many /64 networks inside.

What do compressed and expanded mean?

Expanded shows all eight groups of four hex digits. Compressed (RFC 5952) drops leading zeros and replaces the longest run of zero groups with ::. Both mean the same address.

What is fd00::/8 or fc00::/7?

Unique local addresses (ULA). They are the IPv6 equivalent of private ranges and are not routed on the internet.

Does IPAM Enterprise manage IPv6?

Not today. The portal manages IPv4 address space. This calculator is free for anyone to use.

More free tools

Other tools you may need

Still tracking IPs in a spreadsheet?

IPAM Enterprise keeps every /24, block, customer and circuit in one portal, and checks each assignment for overlaps before it is saved.

Talk to usSee the features