How many addresses are in an IPv6 /29?

An IPv6 /29 contains 2⁹⁹ addresses. The prefix fixes the first 29 bits; the remaining 99 bits identify individual addresses in the block.

How many /64 subnets fit in a /29?

A /29 can be divided into 2³⁵ 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 /29?

A /29 contains 2¹⁹ /48 site allocations. A /48 is the classic size assigned to a business site or campus.

What is the difference between /29 and /30?

A /29 is twice as large as /30. /29 has 2⁹⁹ addresses; /30 has 2⁹⁸. Each step down the prefix number doubles the address count.

How does /29 compare to /28?

A /28 is twice as large as /29. Moving from /29 to /28 adds one more fixed network bit, halving the host portion from 2⁹⁹ to 2¹⁰⁰ addresses.

Is IPv6 /29 the same as IPv4 /29?

No. IPv4 /29 has at most a few thousand hosts. IPv6 /29 still contains 2⁹⁹ addresses — an aggregation size in the IPv6 hierarchy, not a LAN subnet. IPv6 LANs are almost always /64.

IPv6 /29 Subnet Calculator

Results update as you type

A /29 block fixes the first 29 bits of the address, leaving 99 host bits and 2⁹⁹ total addresses. It subdivides into about 2³⁵ /64 LAN subnets. That is also 2¹⁹ /48 site allocations. At the ISP tier, a /29 holds 2³ /32 ISP blocks. Prefixes in this range appear in BGP tables and RIR allocation policies as aggregation blocks above the standard ISP /32.

Prefix length

/128

/29 = 2⁹⁹ addresses (≈ 6.34 × 10²⁹)

Results for 2001:db8::/29

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 /29

Total addresses≈ 6.34 × 10²⁹ addresses

Address typeGlobally routable scope

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

Neighboring /29 subnets

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

Hextet breakdown

20010db8000000000000000000000000

NetworkSplit groupHost

Quick facts for IPv6 /29

Prefix mask: ffff:fff8::
Total addresses: 2⁹⁹
Approx. count: 6.34 × 10²⁹
/64 subnets: 2³⁵

IPv6 /29 reference guideBit split, overview, key facts, sizing tables, design notes, standards, and FAQ

Network / host bit split

netmixhosthosthosthosthosthost

Network bits (29)Split hextetHost bits (99)

Network bits: 29
Host bits: 99
Prefix mask: ffff:fff8::
Total addresses: 2⁹⁹
Approx. count: 6.34 × 10²⁹
/64 subnets: 2³⁵
Addresses formula: 2^99
/64 relationship: 2³⁵ × /64 subnets

Overview

Common use cases

Aggregating ISP /32 allocations in routing tables
Regional provider address planning
Large-scale subnetting study and documentation

Key facts

A /29 fixes 29 network bits and leaves 99 host bits — 2⁹⁹ total addresses.
In network design terms, /29 is typically a large provider aggregation block.
You can subnet a /29 into about 2³⁵ /64 LANs.
At site scale, /29 equals 2¹⁹ /48 allocations.
At ISP scale, /29 contains 2³ /32 blocks.

Design guidance

A /29 belongs in BGP aggregation and RIR allocation planning — not on a VLAN interface. If you are subnetting for a real deployment, work downward: carve /48 or /56 site blocks first, then assign one /64 per LAN. Announcing a single aggregated /29 (or larger) upstream keeps global routing tables manageable.

Practical example

An ISP holding 2001:db8::/29 might announce the entire /29 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
RFC 3849IPv6 Documentation Address Prefix (2001:db8::/32)

Prefix sizing reference

Divide /29 into…

Prefix	Subnets	Addresses each
/30	2	2⁹⁸
/31	4	2⁹⁷
/33	16	2⁹⁵
/37	256	2⁹¹

/29 fits inside…

Supernet	Addresses	/29s inside
/28	2¹⁰⁰	2
/27	2¹⁰¹	4
/25	2¹⁰³	16
/21	2¹⁰⁷	256

Notable /29 networks

2001:db8::/32Documentation prefix (RFC 3849)

Frequently asked questions

Common questions about IPv6 /29 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