Enter an IPv6 address with its prefix length: the calculator gives you the compressed and extended forms, the network, the first and last address, how many /64s the prefix contains, the address type, and the reverse DNS zone, plus ready-to-copy RouterOS commands. The calculation runs in your browser. For IPv4, see the IPv4 IP calculator.

Enter the address with the prefix length, for example 2001:db8::1/64. The extended form is also acceptable.

1. Assign the address to the interface

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With a /64, the router announces the prefix to clients (SLAAC): advertise=yes.

2. Prefix pool to delegate (DHCPv6-PD)

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The pool divides the prefix into /64 subnets to be assigned to customer routers.

Which prefix to use?

  • /64: the size of a single local network. This is the size used for client autoconfiguration (SLAAC): do not use longer prefixes for a LAN;
  • /56: 256 /64 networks, what many operators assign to a residential customer;
  • /48: 65,536 /64 networks, the typical block for a business or site;
  • /127: two addresses, for point-to-point links between routers.

Why are IPv6 networks so large?

Because in IPv6 you do not save addresses: you save prefixes. A LAN is always a /64, even if it has only ten devices, and an operator delegates /64 blocks to customers via DHCPv6 Prefix Delegation. The pool proposed above does exactly this.