IPv6 networking / BROWSER TOOL
IPv6 Subnet Calculator
Find an IPv6 network's exact range and address count. Normalize compressed notation, then preview child subnets without enumerating the addresses inside them.
NORMALIZED NETWORK
- Compressed address
- 2001:db8:1234::1
- Expanded address
- 2001:0db8:1234:0000:0000:0000:0000:0001
- First address in range
- 2001:db8:1234::
- Last address in range
- 2001:db8:1234:ffff:ffff:ffff:ffff:ffff
- Total addresses
- 1,208,925,819,614,629,174,706,176
- Child subnet count
- 65,536
Host bits were cleared to find the containing network. The entered address is shown separately.
These are mathematical endpoints and address counts, not a list of assignable hosts. IPv6 has no broadcast address; special-purpose ranges and subnet-router anycast still affect assignment.
Child subnet preview
| Index | Child network |
|---|---|
| 0 | 2001:db8:1234::/64 |
| 1 | 2001:db8:1234:1::/64 |
| 2 | 2001:db8:1234:2::/64 |
| 3 | 2001:db8:1234:3::/64 |
| 4 | 2001:db8:1234:4::/64 |
| 5 | 2001:db8:1234:5::/64 |
| 6 | 2001:db8:1234:6::/64 |
| 7 | 2001:db8:1234:7::/64 |
Split an IPv6 prefix into a usable address plan
Start with the allocation supplied by your provider or your documented internal prefix. Enter an address inside it and its prefix length. The tool clears host bits to obtain the parent network. If you supply a longer child prefix, it calculates the number of child networks and shows a limited, indexed preview.
Worked example: /48 to /64
The parent 2001:db8:1234::/48 leaves 16 bits available when split into /64s. There are 216, or 65,536, child networks. Index 0 is 2001:db8:1234::/64; index 1 is 2001:db8:1234:1::/64; index 65,535 is 2001:db8:1234:ffff::/64. These documentation addresses are examples, not allocations for public deployment.
Frequently asked questions
Why does a /64 show such a large address count?
IPv6 addresses contain 128 bits. A prefix of length P leaves 128 − P bits, so its mathematical range contains 2128 − P addresses. Counts are calculated with integers rather than rounded floating-point values.
Should I subtract a network and broadcast address?
Do not apply the IPv4 “minus two” shortcut. IPv6 has no broadcast address. That does not make every address suitable for every interface: anycast, address scope and protocol-specific reservations still matter. The calculator deliberately reports total addresses rather than “usable hosts”.
Does a longer prefix work with SLAAC?
Accepting /0 through /128 is an arithmetic capability, not a recommendation for every link. Ethernet SLAAC uses 64-bit interface identifiers; special arrangements such as point-to-point links need their own design. Check your router and address-assignment method before changing prefix lengths.
How are addresses shortened?
Hexadecimal letters use lowercase, leading zeroes in groups are removed, and the longest run of two or more zero groups is compressed. If runs tie, the leftmost wins. A lone zero group stays explicit. IPv4-mapped addresses are displayed with a dotted IPv4 suffix.
Why does the preview stop at 256 rows?
A valid IPv6 split can describe an enormous number of networks. A bounded preview keeps your browser responsive. Change the first subnet index to inspect another part of the allocation; no addresses are scanned or contacted.
Continue the plan
Use the IPv4 subnet calculator for a single IPv4 network, or the VLSM calculator for several networks with different host counts. Keep routing and VLAN isolation explicit in your Proxmox network plan.