Calculate IPv6 networks and subdivide prefixes.
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| First Subnet | Last Subnet | Address Block Size |
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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.
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.
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.
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.
Enter any valid IPv6 address and choose a prefix length (from /48 enterprise networks to /64 standard subnets down to /128 single hosts). The calculator displays the network address, usable range, total host count, and compressed/uncompressed representations instantly. Use it for IPv6 address planning, firewall ACL design, or studying for Cisco/CompTIA certifications.
IPv6 eliminates the need for VLSM in most deployments — each /64 subnet provides 18 quintillion addresses. If you need IPv4 subnetting instead, try our VLSM Calculator or Subnet Calculator. For calculating available bandwidth on a given link speed, use the TCP Throughput Calculator.