Parse IPv6 CIDR blocks: expanded and compressed forms, network range, address count and subnetting.
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About IPv6 subnet calculator
Parses an IPv6 address and prefix length and shows the compressed and fully expanded address, network address, prefix mask, first and last address, total address count, address type (global unicast, unique local, link-local, multicast with scope, and so on), any embedded IPv4 address, and reverse DNS (ip6.arpa) names. A subnetting panel splits the prefix into smaller ones and lists up to 256 of the resulting subnets. All math uses 128-bit integers.
Common uses
- Split a /48 or /56 allocation into /64 subnets
- Expand or compress an IPv6 address to its canonical form
- Check whether an address is link-local, unique local or global
- Get the ip6.arpa zone name for reverse DNS delegation
FAQ
- How is an IPv6 address shortened?
- Leading zeros in each 16-bit group are dropped, and one run of consecutive all-zero groups is replaced with ::. RFC 5952 recommends lowercase hex and compressing the longest run.
- Why is /64 the standard IPv6 subnet size?
- SLAAC and many IPv6 features assume a 64-bit interface identifier, so LAN segments are normally /64. Sites typically receive a /48 or /56 to divide into /64s.
- How many /64 subnets are in a /48?
- 2^(64 - 48) = 65,536. A /56 contains 256 /64 subnets.
- What are fe80::/10 and fc00::/7?
- fe80::/10 is link-local, valid only on a single link. fc00::/7 is unique local address space (in practice fd00::/8), similar in use to private IPv4 ranges.