Subnet Tools
IPv6 Subnet Calculator
Enter an IPv6 address with a prefix length (CIDR). This tool shows the compressed and expanded forms, network, first and last address, block size, address type and reverse DNS, and splits the prefix into smaller subnets.
2001:db8:abcd:12::1/64Documentation
- Network / prefix part
- 2001:0db8:abcd:0012:0000:0000:0000:0001Blue: the 64 network bits. Grey: the 64 host (interface ID) bits.
- Compressed (RFC 5952)
- 2001:db8:abcd:12::1
- Expanded
- 2001:0db8:abcd:0012:0000:0000:0000:0001
- Network
- 2001:db8:abcd:12::/64
- First address
- 2001:db8:abcd:12::
- Last address
- 2001:db8:abcd:12:ffff:ffff:ffff:ffff
- Addresses in this block
- 18,446,744,073,709,551,616(2^64)
- /64 networks inside
- 1(2^0)
- Address type
- Documentation. Reserved for examples and books. Never routed on the internet.
- Reverse DNS name
- 1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.2.1.0.0.d.c.b.a.8.b.d.0.1.0.0.2.ip6.arpa
- Reverse DNS zone
- 2.1.0.0.d.c.b.a.8.b.d.0.1.0.0.2.ip6.arpa
All /64 networks in 2001:db8:abcd:10::/60
16 networksEvery /64 network in the surrounding /60 block. Yours is highlighted.
| Network | First address | Last address |
|---|---|---|
| 2001:db8:abcd:10::/64 | 2001:db8:abcd:10:: | 2001:db8:abcd:10:ffff:ffff:ffff:ffff |
| 2001:db8:abcd:11::/64 | 2001:db8:abcd:11:: | 2001:db8:abcd:11:ffff:ffff:ffff:ffff |
| 2001:db8:abcd:12::/64 | 2001:db8:abcd:12:: | 2001:db8:abcd:12:ffff:ffff:ffff:ffff |
| 2001:db8:abcd:13::/64 | 2001:db8:abcd:13:: | 2001:db8:abcd:13:ffff:ffff:ffff:ffff |
| 2001:db8:abcd:14::/64 | 2001:db8:abcd:14:: | 2001:db8:abcd:14:ffff:ffff:ffff:ffff |
| 2001:db8:abcd:15::/64 | 2001:db8:abcd:15:: | 2001:db8:abcd:15:ffff:ffff:ffff:ffff |
| 2001:db8:abcd:16::/64 | 2001:db8:abcd:16:: | 2001:db8:abcd:16:ffff:ffff:ffff:ffff |
| 2001:db8:abcd:17::/64 | 2001:db8:abcd:17:: | 2001:db8:abcd:17:ffff:ffff:ffff:ffff |
| 2001:db8:abcd:18::/64 | 2001:db8:abcd:18:: | 2001:db8:abcd:18:ffff:ffff:ffff:ffff |
| 2001:db8:abcd:19::/64 | 2001:db8:abcd:19:: | 2001:db8:abcd:19:ffff:ffff:ffff:ffff |
| 2001:db8:abcd:1a::/64 | 2001:db8:abcd:1a:: | 2001:db8:abcd:1a:ffff:ffff:ffff:ffff |
| 2001:db8:abcd:1b::/64 | 2001:db8:abcd:1b:: | 2001:db8:abcd:1b:ffff:ffff:ffff:ffff |
| 2001:db8:abcd:1c::/64 | 2001:db8:abcd:1c:: | 2001:db8:abcd:1c:ffff:ffff:ffff:ffff |
| 2001:db8:abcd:1d::/64 | 2001:db8:abcd:1d:: | 2001:db8:abcd:1d:ffff:ffff:ffff:ffff |
| 2001:db8:abcd:1e::/64 | 2001:db8:abcd:1e:: | 2001:db8:abcd:1e:ffff:ffff:ffff:ffff |
| 2001:db8:abcd:1f::/64 | 2001:db8:abcd:1f:: | 2001:db8:abcd:1f:ffff:ffff:ffff:ffff |
Split 2001:db8:abcd:12::/64 into smaller subnets
16 subnets of /68, each with 1,152,921,504,606,846,976 addresses.
| # | Network | First address | Last address |
|---|---|---|---|
| 1 | 2001:db8:abcd:12::/68 | 2001:db8:abcd:12:: | 2001:db8:abcd:12:fff:ffff:ffff:ffff |
| 2 | 2001:db8:abcd:12:1000::/68 | 2001:db8:abcd:12:1000:: | 2001:db8:abcd:12:1fff:ffff:ffff:ffff |
| 3 | 2001:db8:abcd:12:2000::/68 | 2001:db8:abcd:12:2000:: | 2001:db8:abcd:12:2fff:ffff:ffff:ffff |
| 4 | 2001:db8:abcd:12:3000::/68 | 2001:db8:abcd:12:3000:: | 2001:db8:abcd:12:3fff:ffff:ffff:ffff |
| 5 | 2001:db8:abcd:12:4000::/68 | 2001:db8:abcd:12:4000:: | 2001:db8:abcd:12:4fff:ffff:ffff:ffff |
| 6 | 2001:db8:abcd:12:5000::/68 | 2001:db8:abcd:12:5000:: | 2001:db8:abcd:12:5fff:ffff:ffff:ffff |
| 7 | 2001:db8:abcd:12:6000::/68 | 2001:db8:abcd:12:6000:: | 2001:db8:abcd:12:6fff:ffff:ffff:ffff |
| 8 | 2001:db8:abcd:12:7000::/68 | 2001:db8:abcd:12:7000:: | 2001:db8:abcd:12:7fff:ffff:ffff:ffff |
| 9 | 2001:db8:abcd:12:8000::/68 | 2001:db8:abcd:12:8000:: | 2001:db8:abcd:12:8fff:ffff:ffff:ffff |
| 10 | 2001:db8:abcd:12:9000::/68 | 2001:db8:abcd:12:9000:: | 2001:db8:abcd:12:9fff:ffff:ffff:ffff |
| 11 | 2001:db8:abcd:12:a000::/68 | 2001:db8:abcd:12:a000:: | 2001:db8:abcd:12:afff:ffff:ffff:ffff |
| 12 | 2001:db8:abcd:12:b000::/68 | 2001:db8:abcd:12:b000:: | 2001:db8:abcd:12:bfff:ffff:ffff:ffff |
| 13 | 2001:db8:abcd:12:c000::/68 | 2001:db8:abcd:12:c000:: | 2001:db8:abcd:12:cfff:ffff:ffff:ffff |
| 14 | 2001:db8:abcd:12:d000::/68 | 2001:db8:abcd:12:d000:: | 2001:db8:abcd:12:dfff:ffff:ffff:ffff |
| 15 | 2001:db8:abcd:12:e000::/68 | 2001:db8:abcd:12:e000:: | 2001:db8:abcd:12:efff:ffff:ffff:ffff |
| 16 | 2001:db8:abcd:12:f000::/68 | 2001:db8:abcd:12:f000:: | 2001:db8:abcd:12:ffff:ffff:ffff:ffff |
New to IPv6? Read IPv6 addressing basics.
How it works
An IPv6 address is a 128-bit number, written as eight groups of four hex digits. The prefix length says how many of those bits, from the left, identify the network. The rest identify one interface inside that network.
The calculator keeps the prefix bits and sets every remaining bit to 0 to get the network (and first) address, or to 1 to get the last address. Splitting into subnets borrows extra bits from the host part: each extra bit doubles the number of subnets. Everything runs in your browser.
FAQ
- Why is /64 the normal size for an IPv6 network?
- IPv6 splits an address into a 64-bit network prefix and a 64-bit interface ID. Automatic addressing (SLAAC) needs exactly 64 bits for the interface ID, so almost every LAN, Wi-Fi network and VLAN uses a /64, however few devices it has.
- Why is there no broadcast address or "usable hosts" count?
- IPv6 has no broadcast. It uses multicast instead, so the last address in a block is an ordinary address. And a /64 holds about 18 quintillion addresses, so counting "usable" ones isn't useful: the calculator shows the total.
- What are the rules for shortening an IPv6 address?
- Drop the leading zeros in each group (0db8 becomes db8), and replace one run of all-zero groups with "::". You can use "::" only once, or the address would be ambiguous. The standard form (RFC 5952) uses lowercase letters and shortens the longest run of zeros.
- What prefix will my home or office get?
- Internet providers usually give a home a /56 or /64 and a business a /48. A /48 contains 65,536 /64 networks, and a /56 contains 256.
- What is the reverse DNS zone?
- Reverse DNS for IPv6 lives under ip6.arpa, with each hex digit written backwards and separated by dots. Zones can only be split on whole hex digits, so prefixes that aren't a multiple of 4 round down to the nearest digit.