More detailsNeighboring subnets, expanded address, reverse DNS, and hextet breakdown
Neighboring /64 subnets
- Expanded address
- Compressed address
- Network (expanded)
- Last address (expanded)
- Prefix mask
- Total addresses (exact)
- Reverse DNS (PTR)
- Host bits / network bits
Hextet breakdown
Quick facts for IPv6 /64
- Prefix mask: ffff:ffff:ffff:ffff::
- Total addresses: 2⁶⁴
- Approx. count: 1.84 × 10¹⁹
- /64 subnets: 1
IPv6 /64 reference guideBit split, overview, key facts, sizing tables, design notes, standards, and FAQ
Network / host bit split
- Network bits
- 64
- Host bits
- 64
- Prefix mask
- ffff:ffff:ffff:ffff::
- Total addresses
- 2⁶⁴
- Approx. count
- 1.84 × 10¹⁹
- /64 subnets
- 1
- Addresses formula
- 2^64
- /64 relationship
- exactly one /64
Overview
A /64 is the standard IPv6 subnet — the size of a single LAN. It contains 2⁶⁴ addresses (about 18.4 quintillion), and IPv6 stateless address autoconfiguration (SLAAC) requires a /64 to work. You should almost never make a LAN subnet smaller than /64.
Common use cases
- Every normal LAN / VLAN (one /64 each)
- SLAAC-based address autoconfiguration
- Wi-Fi networks, server segments, container networks
Key facts
- A /64 fixes 64 network bits and leaves 64 host bits — 2⁶⁴ total addresses.
- In network design terms, /64 is typically a standard LAN subnet.
- SLAAC, privacy addresses, and EUI-64 all assume exactly 64 host bits.
Design guidance
Always use /64 for production LANs, Wi-Fi, and container networks. SLAAC, DHCPv6, and neighbor discovery all expect 64 host bits. The enormous address count is intentional — IPv6 design favors flat, spacious subnets over the address conservation mindset of IPv4.
Practical example
2001:db8:abcd:0012::/64 is a typical LAN prefix. A laptop on this subnet might auto-configure 2001:db8:abcd:0012:a1b2:c3d4:e5f6:7890 via SLAAC, while the router uses 2001:db8:abcd:0012::1 as its gateway address.
Related RFCs and standards
- RFC 4291IPv6 Addressing Architecture
- RFC 6177IPv6 Address Assignment to End Sites
- RFC 4862IPv6 Stateless Address Autoconfiguration (SLAAC)
Prefix sizing reference
Frequently asked questions
Common questions about IPv6 /64 blocks, prefix sizes, and use cases.