IPv6 Subnet Calculator
Calculate IPv6 network address, last address, and subnet size from any IPv6 address and prefix length (/64, /48, etc.). Runs in your browser.
IPv6 Subnet Calculator
Enter an IPv6 address and prefix (e.g. 2001:db8::1/64), or use the separate prefix field. Click Get subnet.
Result
| Network (first address) | 2001:db8:: |
|---|---|
| Last address | 2001:db8::ffff:ffff:ffff:ffff |
| Prefix length | /64 |
| Total addresses | 18446744073709551616 |
What Is IPv6 Subnetting?
IPv6 addresses are 128 bits long. Subnetting is done by specifying a prefix length (e.g. /64). The prefix is the leftmost bits that identify the network; the remainder is the interface ID. Unlike IPv4, where we often use /24–/30 for small subnets, IPv6 commonly uses /48 for a site and /64 for a single subnet (e.g. one VLAN). A /64 gives 2^64 host addresses — more than enough for any single broadcast domain. IPv6 has no broadcast address; multicast is used instead.
CIDR notation works the same: 2001:db8::/32 means the first 32 bits are the network. Our subnet calculator is for IPv4; this tool does the same for IPv6. For converting between IPv4 and IPv6 formats use IPv4 to IPv6 converter and IPv6 to IPv4 converter. For validating addresses use IP address validator.
Common IPv6 Prefix Lengths
/32 is often assigned by RIRs to organizations. /48 is a typical allocation for a site; /64 is one subnet (e.g. one LAN). /128 is a single host. This calculator shows the exact network and last address for any prefix. For geolocation of an IPv6 address use IP lookup; for DNS see DNS lookup (AAAA records).
Why IPv6 Subnetting Matters
As the world moves to IPv6, understanding prefix length and allocation helps with firewall rules, routing, and cloud VPCs. Our subnet calculator, CIDR calculator, and IP range calculator are IPv4. This tool covers IPv6. For connectivity tests use ping test and traceroute.
FAQs
What is IPv6 subnetting?
IPv6 uses prefix lengths (e.g. /64, /48) to define subnets. The prefix is the network part; the rest is the interface identifier. /64 is commonly used for LANs.
How many addresses in IPv6 /64?
A /64 leaves 64 bits for hosts, so 2^64 addresses — an enormous number. In practice /64 is one subnet for one LAN or VLAN.
Is there an IPv6 subnet calculator here?
Yes. Enter any IPv6 address and prefix (e.g. 2001:db8::1/64) to get the network address, last address, and total address count. It runs in your browser.
What is the difference between IPv4 and IPv6 subnetting?
IPv4 often uses /24–/30 for small subnets. IPv6 uses much longer prefixes (e.g. /48 for a site, /64 for a subnet); the address space is huge so small host ranges are rarely needed.