IPv6 Subnet Calculator
Calculate an IPv6 prefix's first and last address and size, and split it into /48, /56, /64 or smaller subnets with each one listed in compressed form.
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Input
Calculate and split an IPv6 prefix
Output
2001:db8:abcd::/48
| Network | 2001:db8:abcd::/48 |
|---|---|
| First address | 2001:db8:abcd:: |
| Last address | 2001:db8:abcd:ffff:ffff:ffff:ffff:ffff |
| Addresses | 1,208,925,819,614,629,174,706,176 |
| /64 subnets inside | 65,536 |
| Subnet |
|---|
| 2001:db8:abcd::/64 |
| 2001:db8:abcd:1::/64 |
| 2001:db8:abcd:2::/64 |
| 2001:db8:abcd:3::/64 |
| 2001:db8:abcd:4::/64 |
| 2001:db8:abcd:5::/64 |
| 2001:db8:abcd:6::/64 |
| 2001:db8:abcd:7::/64 |
Every LAN segment should be a /64: SLAAC and privacy addresses need 64 bits of interface identifier. A site typically gets a /48 (65,536 LANs) or a home a /56 (256). /127 is for point-to-point links (RFC 6164). Unlike IPv4 there is no broadcast address to subtract.
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About this tool
Method, assumptions, practical next steps, and limits.
The sizes in practice
A LAN is a /64, always: SLAAC and privacy addresses need the 64-bit interface identifier, and smaller LAN prefixes break them. A site typically receives a /48, which holds 65,536 /64s; a home connection a /56, which holds 256. Point-to-point links may use a /127, per RFC 6164.
Planning with nibbles
Splitting on 4-bit boundaries (/52, /56, /60) keeps each subnet's digits aligned with hex characters, so 2001:db8:abcd:1200::/56 and its /64s read naturally. There is no broadcast address in IPv6 and no host count arithmetic to subtract.
