IPv6 subnet calculator
Enter an IPv6 address with a prefix length, for example 2001:db8:abcd::/48. You get the network, the first and last address, how many addresses it holds and how many /64 subnets fit in it. It runs in your browser; nothing is sent anywhere.
The prefix field is used only when the address has no /.
- Compressed address
- 2001:db8:abcd:12::5
- Expanded address
- 2001:0db8:abcd:0012:0000:0000:0000:0005
- Prefix
- /48
- Network
- 2001:db8:abcd::/48
- First address
- 2001:db8:abcd::
- Last address
- 2001:db8:abcd:ffff:ffff:ffff:ffff:ffff
- Total addresses
- 1,208,925,819,614,629,174,706,176
- /64 subnets inside
- 65,536
- Address type
- Documentation (2001:db8::/32)
Questions
How many addresses are in a /64?
About 18 quintillion (2^64). A /64 is the standard size of one network segment, so even a single LAN has far more addresses than it will ever use.
Why do LANs use /64?
Automatic address configuration (SLAAC) needs the last 64 bits for the interface identifier, so a subnet smaller than /64 breaks it. Providers typically give a site a /48 or /56, which holds 65,536 or 256 subnets of /64.
What does :: mean in an address?
It stands for one or more groups of zeros. It can appear only once in an address, which is why 2001:db8:0:0:1:0:0:1 is written 2001:db8::1:0:0:1.
Is there a broadcast address in IPv6?
No. IPv6 uses multicast instead. The “last address” shown here is simply the highest address in the prefix.