More detailsNeighboring subnets, expanded address, reverse DNS, and hextet breakdown
Neighboring /79 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 /79
- Prefix mask: ffff:ffff:ffff:ffff:fffe::
- Total addresses: 2⁴⁹
- Approx. count: 5.63 × 10¹⁴
- /64 subnets: —
IPv6 /79 reference guideBit split, overview, key facts, sizing tables, design notes, standards, and FAQ
Network / host bit split
netnetnetnetmixhosthosthost
Network bits (79)Split hextetHost bits (49)
- Network bits
- 79
- Host bits
- 49
- Prefix mask
- ffff:ffff:ffff:ffff:fffe::
- Total addresses
- 2⁴⁹
- Approx. count
- 5.63 × 10¹⁴
- /64 subnets
- —
- Addresses formula
- 2^49
- /64 relationship
- smaller than a /64
Overview
A /79 leaves 49 host bits (2⁴⁹ addresses). It is smaller than a /64 LAN and appears in specialized schemes — for example /96 embeds a 32-bit IPv4 address for NAT64 or IPv4-mapped addressing.
Common use cases
- NAT64 and IPv4-embedded addressing study
- Specialized translation gateway design
- Protocol documentation and examples
Key facts
- A /79 fixes 79 network bits and leaves 49 host bits — 2⁴⁹ total addresses.
- In network design terms, /79 is typically a specialized sub-/64 block.
- A /79 is 1/2¹⁵ of a standard /64 LAN subnet.
Design guidance
A /79 is a specialized size, not a general LAN substitute. Production VLANs should remain /64. Use /79 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::1/79 might number a small segment with 2⁴⁹ 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 /79 blocks, prefix sizes, and use cases.