Split any IPv6 prefix into subnets, count the /48s and /64s inside it, and get the subnet list instantly. Everything runs in your browser.
/64 networks inside the prefix
Canonical form
How many subnets fit inside each common IPv6 prefix:
| Prefix | Typical use | /48s | /56s | /64s |
|---|---|---|---|---|
| /29 | Default RIPE LIR allocation | 524,288 | 134,217,728 | 34,359,738,368 |
| /32 | Smaller LIR allocation | 65,536 | 16,777,216 | 4,294,967,296 |
| /40 | Large sub-allocation | 256 | 65,536 | 16,777,216 |
| /44 | Multi-site operator block | 16 | 4,096 | 1,048,576 |
| /48 | One end site (RIPE recommendation) | 1 | 256 | 65,536 |
| /56 | Residential customer | - | 1 | 256 |
| /64 | One network segment (LAN/VLAN) | - | - | 1 |
65,536. Each additional prefix bit doubles the count: a /48 split to /64 gives 2 to the power 16 subnets.
65,536 as well, for the same reason: 48 minus 32 is 16 bits, and 2 to the power 16 is 65,536.
RIPE best practice (ripe-690) recommends a /48 per end site, with /56 common for residential users.
Never assign smaller than /64 to a network segment, since SLAAC requires a full /64.
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