IPv6 /44 Prefix ReferenceIPv6
Sixteen site allocations under one aggregate: a /44 carries 1,048,576 /64 subnets and hands a mid-size organization a /48 for every major location while leaving headroom to spare. It is the working compromise between a lone /48 and a provider-scale /40.
/44 facts at a glance
- Total addresses
- 19,342,813,113,834,066,795,298,816 (284)
- /64 subnets inside
- 1,048,576
- Host/interface bits
- 84
- Example network
- 2001:db8::/44
- First address
- 2001:db8::
- Last address
- 2001:db8:f:ffff:ffff:ffff:ffff:ffff
- Typical role
- Enterprise with many routed sites
A /44 in documentation space
Using 2001:db8::/32 (RFC 3849 documentation space) aligned to its own boundary, a /44 occupies:
| Block | First address | Last address |
|---|---|---|
| 2001:db8::/44 | 2001:db8:: | 2001:db8:f:ffff:ffff:ffff:ffff:ffff |
How an IPv6 /44 prefix works
A /44 prefix pins the first 44 bits of a 128-bit address, leaving 84 bits free. That free portion holds 284 = 19,342,813,113,834,066,795,298,816 distinct addresses, and every such block begins at a multiple of that size. Because each subnet should be a /64, the 20 middle bits between the prefix and the /64 boundary give 1,048,576 subnets to hand out.
Where /44 is used
- Enterprises running up to sixteen sites, each addressed from its own /48.
- Providers delegating beefier blocks to demanding business customers.
- Organizations consolidating scattered /48s into a single routable aggregate.
The split table is tidy: sixteen /48s, four /46s, or 256 /52s — every hop nibble-aligned.
With over a million /64s inside, capacity questions dissolve; routing and delegation hygiene deserve the attention instead.
Frequently asked questions
How many addresses does an IPv6 /44 have?
19,342,813,113,834,066,795,298,816 — 2^84, eighty-four host bits wide.
How many /48s are in a /44?
Sixteen. Four bits separate the prefixes, so a /44 is the classic site block multiplied sixteen times over.
Is a /44 bigger than a /48?
Yes, by a factor of sixteen. Shorter prefix, bigger block — each bit you shed doubles the space.
How many /64 subnets can I build from a /44?
1,048,576 standard subnets, which comfortably covers a multi-building campus with room for decades of growth.
Open this prefix in the calculator
Open 2001:db8::/44 in the IPv6 calculator