IPv6 CIDR to Range
Convert an IPv6 CIDR block to its first and last address and address count.
Each block shows the first and last address and how many addresses it holds.
Continue your work
- IPv6 Range to CIDR — Turn a range back into CIDR blocks.
- IPv6 Subnet Calculator — Split a prefix into smaller subnets.
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Clear instructions
Find steps, examples and limitations below.
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How to use the IPv6 CIDR to Range
Convert an IPv6 CIDR block to its first and last address and address count.
- 1 Enter one IPv6 CIDR block per line, such as 2001:db8::/48.
- 2 Read the first address, last address and address count for each block.
- 3 Copy the ranges for firewall rules or documentation.
Example and practical tips
2001:db8:abcd:12::/64 runs from 2001:0db8:abcd:0012:0000:0000:0000:0000 to 2001:0db8:abcd:0012:ffff:ffff:ffff:ffff, 2^64 addresses.
Frequently asked questions
What does the prefix length mean?
It is the number of leading bits fixed for the network; the rest vary. A /64 has 64 fixed bits and 64 host bits.
Why is /64 so common?
IPv6 automatic addressing (SLAAC) expects /64 subnets, so almost every LAN uses one.
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