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IPv6 Subnet Calculator

Calculate IPv6 networks and subdivide prefixes.

Network Prefix

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Prefix Length

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Subnet Count

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Total Addresses

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Subnet Details

First Subnet Last Subnet Address Block Size
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How to use the ipv6 subnet calculator

  1. Paste any IPv6 address with a /N prefix, e.g. 2001:db8:abcd::/48.
  2. The tool returns the network range, the host portion size, and standard /48, /56, /64 sub-allocations.
  3. Use it to plan an enterprise IPv6 plan or to verify a /64 LAN before deployment.

Frequently asked questions

Why is /64 the standard IPv6 subnet size?

SLAAC, the IPv6 stateless address autoconfiguration mechanism, derives the host portion from a 64-bit Interface Identifier. A /64 is required for SLAAC to work as designed.

What is the difference between /48 and /56 IPv6 allocation?

A /48 gives an organisation 65,536 /64 subnets — typical for a large company. A /56 gives 256 /64s — typical for a residential or small-business ISP allocation.

How are link-local fe80::/10 addresses used?

Link-local addresses are automatically configured on every IPv6 interface and used for neighbour discovery, router advertisement and OSPFv3 adjacencies. They never leave the local segment.

Do I still need NAT in IPv6?

Generally no. IPv6 provides enough globally routable addresses to give every device one. Firewalls still enforce access control; address translation is no longer required for scarcity.