More detailsNeighboring subnets, expanded address, reverse DNS, and hextet breakdown
Neighboring /54 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 /54
- Prefix mask: ffff:ffff:ffff:fc00::
- Total addresses: 2⁷⁴
- Approx. count: 1.89 × 10²²
- /64 subnets: 2¹⁰
IPv6 /54 reference guideBit split, overview, key facts, sizing tables, design notes, standards, and FAQ
Network / host bit split
- Network bits
- 54
- Host bits
- 74
- Prefix mask
- ffff:ffff:ffff:fc00::
- Total addresses
- 2⁷⁴
- Approx. count
- 1.89 × 10²²
- /64 subnets
- 2¹⁰
- Addresses formula
- 2^74
- /64 relationship
- 2¹⁰ × /64 subnets
Overview
A /54 block fixes the first 54 bits of the address, leaving 74 host bits and 2⁷⁴ total addresses. It subdivides into 2¹⁰ /64 LAN subnets. A /54 is a site or subscriber delegation size — larger than a single /64 LAN but smaller than the classic /48 site block.
Common use cases
- Business site or campus delegation
- ISP customer prefix assignment
- Subdividing into /64 VLANs and LANs
Key facts
- A /54 fixes 54 network bits and leaves 74 host bits — 2⁷⁴ total addresses.
- In network design terms, /54 is typically a medium site or business delegation.
- You can subnet a /54 into 2¹⁰ /64 LANs.
Design guidance
A /54 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 2¹⁰ available /64s, you have ample room for guest networks, IoT, management, and lab segments.
Practical example
Suppose your ISP delegates 2001:db8:abcd:1200::/54 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 2¹⁰ 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 /54 blocks, prefix sizes, and use cases.