More detailsNeighboring subnets, expanded address, reverse DNS, and hextet breakdown
Neighboring /24 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 /24
- Prefix mask: ffff:ff00::
- Total addresses: 2¹⁰⁴
- Approx. count: 2.03 × 10³¹
- /64 subnets: 2⁴⁰
IPv6 /24 reference guideBit split, overview, key facts, sizing tables, design notes, standards, and FAQ
Network / host bit split
- Network bits
- 24
- Host bits
- 104
- Prefix mask
- ffff:ff00::
- Total addresses
- 2¹⁰⁴
- Approx. count
- 2.03 × 10³¹
- /64 subnets
- 2⁴⁰
- Addresses formula
- 2^104
- /64 relationship
- 2⁴⁰ × /64 subnets
Overview
A /24 in IPv6 is still an enormous block — 2¹⁰⁴ addresses — but it sits at the smaller end of the global allocation hierarchy. It can hold 256 /32 ISP blocks or 2⁴⁰ standard /64 LANs. Do not confuse it with an IPv4 /24 (254 hosts); in IPv6 a /24 is a major aggregation prefix, not a home network.
Common use cases
- Mid-tier address aggregation in routing documentation
- Grouping /32 allocations for regional providers
- Subnetting exercises and certification study
Key facts
- A /24 fixes 24 network bits and leaves 104 host bits — 2¹⁰⁴ total addresses.
- In network design terms, /24 is typically a large provider aggregation block.
- You can subnet a /24 into about 2⁴⁰ /64 LANs.
- At site scale, /24 equals about 2²⁴ /48 allocations.
- At ISP scale, /24 contains 2⁸ /32 blocks.
Design guidance
A /24 belongs in BGP aggregation and RIR allocation planning — not on a VLAN interface. If you are subnetting for a real deployment, work downward: carve /48 or /56 site blocks first, then assign one /64 per LAN. Announcing a single aggregated /24 (or larger) upstream keeps global routing tables manageable.
Practical example
An ISP holding 2001:db8::/24 might announce the entire /24 to upstream providers as one BGP route, then delegate /48 blocks such as 2001:db8:0001::/48 and 2001:db8:0002::/48 to business customers. Each customer subnets their /48 into /64 LANs.
Related RFCs and standards
- RFC 4291IPv6 Addressing Architecture
- RFC 3849IPv6 Documentation Address Prefix (2001:db8::/32)
Prefix sizing reference
Notable /24 networks
2001:db8::/32Documentation prefix (RFC 3849)
Frequently asked questions
Common questions about IPv6 /24 blocks, prefix sizes, and use cases.