How many addresses are in an IPv6 /33?

An IPv6 /33 contains 2⁹⁵ addresses. The prefix fixes the first 33 bits; the remaining 95 bits identify individual addresses in the block.

How many /64 subnets fit in a /33?

A /33 can be divided into 2³¹ standard /64 LAN subnets. Each /64 holds 2⁶⁴ addresses, so the combined block is effectively inexhaustible for normal use.

How many /48 site allocations are in a /33?

A /33 contains 2¹⁵ /48 site allocations. A /48 is the classic size assigned to a business site or campus.

When would an organization receive a /33?

A /33 is assigned when an organization needs more address space than a single /48 but does not qualify for a full ISP-style /32. It is common for large enterprises with many branch offices.

What is the difference between /33 and /34?

A /33 is twice as large as /34. /33 has 2⁹⁵ addresses; /34 has 2⁹⁴. Each step down the prefix number doubles the address count.

How does /33 compare to /32?

A /32 is twice as large as /33. Moving from /33 to /32 adds one more fixed network bit, halving the host portion from 2⁹⁵ to 2⁹⁶ addresses.

IPv6 /33 Subnet Calculator

Results update as you type

A /33 block fixes the first 33 bits of the address, leaving 95 host bits and 2⁹⁵ total addresses. It subdivides into about 2³¹ /64 LAN subnets. That is also 2¹⁵ /48 site allocations. A /33 sits between the standard ISP /32 and the site /48 — useful when an organization needs more than one /48 but less than a full /32.

Prefix length

/128

/33 = 2⁹⁵ addresses (≈ 3.96 × 10²⁸)

Results for 2001:db8:8000::/33

Documentation (RFC 3849)Global scope

Network / prefixThe first address — identifies the subnet itself

First addressSubnet-router anycast; first address in the block

Last addressThe highest address in this block

Prefix maskEquivalent to /33

Total addresses≈ 3.96 × 10²⁸ addresses

Address typeGlobally routable scope

More detailsNeighboring subnets, expanded address, reverse DNS, and hextet breakdown

Neighboring /33 subnets

Expanded address
Compressed address
Network (expanded)
Last address (expanded)
Prefix mask
Total addresses (exact)
Reverse DNS (PTR)
Host bits / network bits

Hextet breakdown

20010db8abcd00000000000000000000

NetworkSplit groupHost

Quick facts for IPv6 /33

Prefix mask: ffff:ffff:8000::
Total addresses: 2⁹⁵
Approx. count: 3.96 × 10²⁸
/64 subnets: 2³¹

IPv6 /33 reference guideBit split, overview, key facts, sizing tables, design notes, standards, and FAQ

Network / host bit split

netnetmixhosthosthosthosthost

Network bits (33)Split hextetHost bits (95)

Network bits: 33
Host bits: 95
Prefix mask: ffff:ffff:8000::
Total addresses: 2⁹⁵
Approx. count: 3.96 × 10²⁸
/64 subnets: 2³¹
Addresses formula: 2^95
/64 relationship: 2³¹ × /64 subnets

Overview

Common use cases

Enterprise or ISP allocations above site size
Multi-site organizations needing several /48s
Address renumbering and growth planning

Key facts

A /33 fixes 33 network bits and leaves 95 host bits — 2⁹⁵ total addresses.
In network design terms, /33 is typically a enterprise or multi-site allocation.
You can subnet a /33 into about 2³¹ /64 LANs.
At site scale, /33 equals 2¹⁵ /48 allocations.

Design guidance

A /33 suits organizations that have outgrown a single /48 but do not need a full /32 ISP allocation. Plan your addressing scheme before delegating: assign one /48 (or smaller) per major site, then subnet each site into /64 LANs. Document your nibble boundaries so future growth does not force renumbering.

Practical example

An ISP holding 2001:db8:abcd::/33 might announce the entire /33 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

Prefix sizing reference

Divide /33 into…

Prefix	Subnets	Addresses each
/34	2	2⁹⁴
/35	4	2⁹³
/37	16	2⁹¹
/41	256	2⁸⁷

/33 fits inside…

Supernet	Addresses	/33s inside
/32	2⁹⁶	2
/31	2⁹⁷	4
/29	2⁹⁹	16
/25	2¹⁰³	256

Frequently asked questions

Common questions about IPv6 /33 blocks, prefix sizes, and use cases.

Common IPv6 prefix sizes

/3 /12 /16 /20 /24 /28 /32 /36 /40 /44 /48 /52 /56 /60 /64 /80 /96 /112 /120 /124 /126 /127 /128