IPv6 Subnet Calculator
Link-local
fe80::/10RFC 4291 link-local. Every IPv6 interface has one, it is what neighbour discovery runs over, and no router forwards it.
Not announced in BGP, so there is no operator or routing to show.
RFC 4291 link-local. Every IPv6 interface has one, it is what neighbour discovery runs over, and no router forwards it.
fe80::
fe80:0000:0000:0000:0000:0000:0000:0000
fe80::
febf:ffff:ffff:ffff:ffff:ffff:ffff:ffff
ffc0::
/10
e.f.ip6.arpa
Covering /8 zone — a /10 is not nibble-aligned
0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.e.f.ip6.arpa
Network Information
3.32 × 10³⁵
1.8 × 10¹⁶
fe80:: – febf:ffff:ffff:ffff:ffff:ffff:ffff:ffff
IPv6 Prefix Cheat Sheet
| Prefix | Addresses | /64 subnets | Netmask | Typical use |
|---|---|---|---|---|
| /128 | 1 | — | ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff | A single address — a host route or a loopback |
| /127 | 2 | — | ffff:ffff:ffff:ffff:ffff:ffff:ffff:fffe | Point-to-point link between two routers (RFC 6164) |
| /126 | 4 | — | ffff:ffff:ffff:ffff:ffff:ffff:ffff:fffc | Four addresses — the IPv4 /30 habit carried over to a router link |
| /124 | 16 | — | ffff:ffff:ffff:ffff:ffff:ffff:ffff:fff0 | 16 addresses — small static assignment |
| /120 | 256 | — | ffff:ffff:ffff:ffff:ffff:ffff:ffff:ff00 | 256 addresses — the IPv6 size of an IPv4 /24, used for static server ranges |
| /112 | 65,536 | — | ffff:ffff:ffff:ffff:ffff:ffff:ffff:0 | Sometimes used for numbered infrastructure links |
| /96 | 4,294,967,296 | — | ffff:ffff:ffff:ffff:ffff:ffff:: | Translation and mapping prefixes (::ffff:0:0/96, 64:ff9b::/96) sit here |
| /80 | 281,474,976,710,656 | — | ffff:ffff:ffff:ffff:ffff:: | Below the LAN boundary — breaks SLAAC, occasionally seen in labs |
| /64 | 1.84 × 10¹⁹ | 1 | ffff:ffff:ffff:ffff:: | One LAN. The standard subnet size, and the smallest that SLAAC works on |
| /60 | 2.95 × 10²⁰ | 16 | ffff:ffff:ffff:fff0:: | Smaller residential assignment — 16 /64 LANs |
| /56 | 4.72 × 10²¹ | 256 | ffff:ffff:ffff:ff00:: | The usual residential or small-business assignment — 256 /64 LANs |
| /52 | 7.55 × 10²² | 4,096 | ffff:ffff:ffff:f000:: | Nibble-aligned split of a site /48, tidy for reverse DNS |
| /48 | 1.2 × 10²⁴ | 65,536 | ffff:ffff:ffff:: | The standard site allocation — one organisation or campus, 65,536 /64s |
| /44 | 1.93 × 10²⁵ | 1,048,576 | ffff:ffff:fff0:: | Large enterprise or a POP inside an ISP |
| /40 | 3.09 × 10²⁶ | 16,777,216 | ffff:ffff:ff00:: | Aggregation boundary inside a large ISP; a nibble above /44 |
| /36 | 4.95 × 10²⁷ | 268,435,456 | ffff:ffff:f000:: | Regional slice of an ISP allocation |
| /32 | 7.92 × 10²⁸ | 4,294,967,296 | ffff:ffff:: | The standard ISP allocation — enough for 65,536 customer /48s |
| /29 | 6.33 × 10²⁹ | 34,359,738,368 | ffff:fff8:: | Common RIR allocation to an ISP, sized to allow later growth |
| /28 | 1.26 × 10³⁰ | 68,719,476,736 | ffff:fff0:: | Large ISP allocation from an RIR |
| /24 | 2.02 × 10³¹ | 1,099,511,627,776 | ffff:ff00:: | Very large ISP or national network allocation |
| /20 | 3.24 × 10³² | 17,592,186,044,416 | ffff:f000:: | Sub-allocation inside an RIR |
| /16 | 5.19 × 10³³ | 281,474,976,710,656 | ffff:: | Very large block; 2002::/16 (6to4) and ff00::/8's neighbours live at this scale |
| /12 | 8.3 × 10³⁴ | 4.5 × 10¹⁵ | fff0:: | An RIR's allocation from IANA |
| /10 | 3.32 × 10³⁵ | 1.8 × 10¹⁶ | ffc0:: | fe80::/10, link-local — every interface has one |
| /7 | 2.65 × 10³⁶ | 1.44 × 10¹⁷ | fe00:: | fc00::/7, the unique local (ULA) block |
| /3 | 4.25 × 10³⁷ | 2.3 × 10¹⁸ | e000:: | 2000::/3, the global unicast block the registries allocate from |
| /0 | 3.4 × 10³⁸ | 1.84 × 10¹⁹ | :: | Default route — matches every IPv6 address |
Quick Reference
How to Use
Enter an IPv6 address and prefix length above — or paste 2001:db8::/48 straight in — to see the prefix boundaries, how many /64s it holds, its reverse DNS zone, and what kind of address it is.
Why /64 Matters
A /64 is the standard IPv6 subnet, and the smallest one stateless autoconfiguration (SLAAC) works on: the low 64 bits are the interface identifier, which hosts assign themselves. Subnet above /64, never below it.
Common Prefix Sizes
/32 is a typical ISP allocation, /48 goes to a site or organisation, /56 to a home or small business, and /64 to a single LAN. Router-to-router links usually use /127.