How many addresses exist in an IPv6 /64 prefix?

A /64 prefix provides 2^64 addresses, which equals 18,446,744,073,709,551,616 (18.4 quintillion) unique IP addresses. It is the standard single LAN subnet size in IPv6 architecture.

What is IPv6 zero compression (::)?

Per RFC 5952, consecutive 16-bit blocks of all zeros can be compressed into a double colon (::). This compression can only be applied once in an address to avoid ambiguity.

IPv6 Subnet Calculator & Address Expander

Calculate IPv6 network prefixes, expand or compress 128-bit addresses, and determine subnet host capacity.

IPv6 Address (Compressed or Expanded)

Prefix Length (CIDR)

Calculated IPv6 Architecture Global Unicast (2000::/3)

Full Expanded Notation (RFC 4291)

2001:0db8:85a3:0000:0000:8a2e:0370:7334

RFC 5952 Canonical Compressed Form

2001:db8:85a3::8a2e:370:7334

Network Prefix

2001:db8:85a3:: /64

Total Subnet Capacity

18,446,744,073,709,551,616 (2⁶⁴)

Standard Subnets Contained (/64s)

1 Subnet

IPv6 Address Scope

Public Global Internet

🌐 Architecture Standard: In IPv6, stateless address autoconfiguration (SLAAC) strictly mandates /64 subnets. Never subnet LANs smaller than /64 to ensure host compatibility.

Understanding IPv6 Subnetting & Address Architecture

Internet Protocol version 6 (RFC 8200) replaces the 32-bit address space of IPv4 with a massive 128-bit address space, providing 3.4 × 10³⁸ unique addresses and eliminating the need for NAT.

Common IPv6 Prefix Allocation Standards

Prefix Length	Addresses	Standard Allocation Purpose
`/32`	2⁹⁶ addresses	Internet Service Providers (ISPs) and Telcos
`/48`	2⁸⁰ addresses (65,536 × /64 subnets)	Enterprise business networks and data centers
`/56`	2⁷² addresses (256 × /64 subnets)	Residential broadband and small branch offices
`/64`	2⁶⁴ addresses (18.4 quintillion)	Standard single broadcast domain / LAN subnet
`/128`	1 address	Single host loopback or router interface address