More detailsNeighboring subnets, expanded address, reverse DNS, and hextet breakdown
Neighboring /105 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 /105
- Prefix mask: ffff:ffff:ffff:ffff:ffff:ffff:ff80:0
- Total addresses: 2²³
- Approx. count: 8.39 × 10⁶
- /64 subnets: —
IPv6 /105 reference guideBit split, overview, key facts, sizing tables, design notes, standards, and FAQ
Network / host bit split
netnetnetnetnetnetmixhost
Network bits (105)Split hextetHost bits (23)
- Network bits
- 105
- Host bits
- 23
- Prefix mask
- ffff:ffff:ffff:ffff:ffff:ffff:ff80:0
- Total addresses
- 2²³
- Approx. count
- 8.39 × 10⁶
- /64 subnets
- —
- Addresses formula
- 2^23
- /64 relationship
- smaller than a /64
Overview
A /105 provides 2²³ addresses — a tightly scoped segment much smaller than a /64. It is occasionally used for management networks or lab exercises where a full /64 is unnecessary.
Common use cases
- Constrained management or out-of-band segments
- Lab networks with a fixed address budget
- Documentation of smaller-than-/64 designs
Key facts
- A /105 fixes 105 network bits and leaves 23 host bits — 2²³ total addresses.
- In network design terms, /105 is typically a constrained management or lab segment.
- A /105 is 1/2⁴¹ of a standard /64 LAN subnet.
Design guidance
A /105 can work for small management VLANs, out-of-band networks, or certification lab exercises where you deliberately cap the host count. For router interconnects, prefer /127 (RFC 6164) over /105. For ordinary LANs, stay with /64 regardless of how small the segment feels.
Practical example
In a lab, 2001:db8:abcd:0012::1/105 might number a small segment with 2²³ 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 /105 blocks, prefix sizes, and use cases.