IPv6 Subnet Calculator
Enter an IPv6 address and prefix length to get the network, address range, expanded form and how many subnets it holds.
- Network
- 2001:db8:abcd:12::/64
- Expanded network
- 2001:0db8:abcd:0012:0000:0000:0000:0000
- First address
- 2001:db8:abcd:12::
- Last address
- 2001:db8:abcd:12:ffff:ffff:ffff:ffff
- Total addresses
- 2^64 (18,446,744,073,709,551,616)
- /64 subnets
- 2^0
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Reading an IPv6 prefix
IPv6 addresses are 128 bits, written as eight groups of four hex digits. A prefix like /64 means the first 64 bits identify the network and the remaining 64 address hosts, which is the standard size for a single LAN. ISPs commonly delegate a /56 or /48 to each customer, giving them 256 or 65,536 separate /64 subnets.
Why the numbers are so large
Every bit of host space doubles the count, so even a single /64 holds 2^64 addresses, far more than the entire IPv4 internet. That is why IPv6 planning is about assigning prefixes cleanly rather than conserving individual addresses.
Where this fits in running an ISP
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