More detailsNeighboring subnets, expanded address, reverse DNS, and hextet breakdown
Neighboring /48 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 /48
- Prefix mask: ffff:ffff:ffff::
- Total addresses: 2⁸⁰
- Approx. count: 1.21 × 10²⁴
- /64 subnets: 2¹⁶
IPv6 /48 reference guideBit split, overview, key facts, sizing tables, design notes, standards, and FAQ
Network / host bit split
- Network bits
- 48
- Host bits
- 80
- Prefix mask
- ffff:ffff:ffff::
- Total addresses
- 2⁸⁰
- Approx. count
- 1.21 × 10²⁴
- /64 subnets
- 2¹⁶
- Addresses formula
- 2^80
- /64 relationship
- 2¹⁶ × /64 subnets
Overview
A /48 is the classic site allocation in IPv6. It gives an organization 65,536 /64 subnets — far more than almost any single site will ever need. RIRs and ISPs commonly assign a /48 to each business customer, and RFC 6177 recommends it as a reasonable default site size.
Common use cases
- Standard business / site allocation
- Enterprise campus with many VLANs
- Multi-building organizations (one /64 per VLAN)
Key facts
- A /48 fixes 48 network bits and leaves 80 host bits — 2⁸⁰ total addresses.
- In network design terms, /48 is typically a standard site allocation.
- You can subnet a /48 into 2¹⁶ /64 LANs.
Design guidance
A /48 is a practical site or campus delegation. Give each VLAN, Wi-Fi SSID, and security zone its own /64 — do not subnet below /64 on production LANs. With 2¹⁶ available /64s, you have ample room for guest networks, IoT, management, and lab segments.
Practical example
Suppose your ISP delegates 2001:db8:abcd::/48 to your edge router. You could assign 2001:db8:abcd:0012::/64 to your main LAN, 2001:db8:abcd:0013::/64 to guest Wi-Fi, and 2001:db8:abcd:0014::/64 to IoT — using only 3 of the 2¹⁶ available /64 subnets.
Related RFCs and standards
- RFC 4291IPv6 Addressing Architecture
- RFC 6177IPv6 Address Assignment to End Sites
- RFC 3633IPv6 Prefix Options for DHCPv6 Prefix Delegation
Prefix sizing reference
Frequently asked questions
Common questions about IPv6 /48 blocks, prefix sizes, and use cases.