More detailsNeighboring subnets, expanded address, reverse DNS, and hextet breakdown
Neighboring /80 subnets
- Expanded address
- Compressed address
- Network (expanded)
- Last address (expanded)
- Prefix mask
- Total addresses (exact)
- Reverse DNS (PTR)
- Host bits / network bits
Hextet breakdown
20010db8abcd00120000000000000001
NetworkSplit groupHost
Quick facts for IPv6 /80
- Prefix mask: ffff:ffff:ffff:ffff:ffff::
- Total addresses: 2⁴⁸
- Approx. count: 2.81 × 10¹⁴
- /64 subnets: —
IPv6 /80 reference guideBit split, overview, key facts, sizing tables, design notes, standards, and FAQ
Network / host bit split
netnetnetnetnethosthosthost
Network bits (80)Split hextetHost bits (48)
- Network bits
- 80
- Host bits
- 48
- Prefix mask
- ffff:ffff:ffff:ffff:ffff::
- Total addresses
- 2⁴⁸
- Approx. count
- 2.81 × 10¹⁴
- /64 subnets
- —
- Addresses formula
- 2^48
- /64 relationship
- smaller than a /64
Overview
A /80 leaves 48 host bits — coincidentally the size of a MAC address. It contains 2⁴⁸ addresses. It is rarely used for LANs (which should be /64) but appears in specialized addressing schemes.
Common use cases
- Specialized / non-SLAAC addressing
- Documentation of sub-/64 structure
Key facts
- A /80 fixes 80 network bits and leaves 48 host bits — 2⁴⁸ total addresses.
- In network design terms, /80 is typically a specialized sub-/64 block.
- A /80 is 1/2¹⁶ of a standard /64 LAN subnet.
Design guidance
A /80 is a specialized size, not a general LAN substitute. Production VLANs should remain /64. Use /80 only when a protocol or design explicitly calls for it — for example /96 in NAT64 translation — or in controlled lab environments.
Practical example
In a lab, 2001:db8:abcd:0012::1/80 might number a small segment with 2⁴⁸ addresses. In production, you would normally expand this to a full /64 unless you have a documented exception.
Prefix sizing reference
Frequently asked questions
Common questions about IPv6 /80 blocks, prefix sizes, and use cases.