# IPv6 /48 Prefix – 65,536 /64 Subnets Explained

> An IPv6 /48 prefix spans 65,536 /64 subnets (1,208,925,819,614,629,174,706,176 addresses). Examples, roles and FAQs for planning IPv6 networks.

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# IPv6 /48 Prefix ReferenceIPv6

The classic site allocation: a /48 wraps 65,536 /64 subnets into one block, historically the standard gift to any business that asked. Policy has loosened since, but the /48 remains the archetype of a company-sized prefix.

An IPv6 /48 prefix contains 1,208,925,819,614,629,174,706,176 addresses, which splits into 65,536 standard /64 subnets.

## /48 facts at a glance

- **Total addresses:** 1,208,925,819,614,629,174,706,176 (280)
- **/64 subnets inside:** 65,536
- **Host/interface bits:** 80
- **Example network:** 2001:db8::/48
- **First address:** 2001:db8::
- **Last address:** 2001:db8:0:ffff:ffff:ffff:ffff:ffff
- **Typical role:** Standard site allocation (routing prefix)

## A /48 in documentation space

Using `2001:db8::/32` (RFC 3849 documentation space) aligned to its own boundary, a /48 occupies:

| Block | First address | Last address |
| --- | --- | --- |
| 2001:db8::/48 | 2001:db8:: | 2001:db8:0:ffff:ffff:ffff:ffff:ffff |

## How an IPv6 /48 prefix works

A /48 prefix pins the first 48 bits of a 128-bit address, leaving 80 bits free. That free portion holds 280 = 1,208,925,819,614,629,174,706,176 distinct addresses, and every such block begins at a multiple of that size. Because each subnet should be a /64, the 16 middle bits between the prefix and the /64 boundary give 65,536 subnets to hand out.

## Where /48 is used

- Enterprise sites carrying their own /48 under one corporate aggregate.
- Hosting providers subdividing a /48 into customer /56s or /64s.
- Multi-VLAN campuses that want every segment routed without NAT.

Early guidance (RFC 3177) urged giving every site a /48; RFC 6177 relaxed that advice toward right-sizing, so businesses today commonly receive /48s or /56s depending on need.

## Frequently asked questions

**How many /64s fit in a /48?**

65,536. Sixteen bits separate the prefixes, so a /48 also equals 256 blocks of /56.

**Is a /48 still the standard business allocation?**

It depends on the provider: since RFC 6177 replaced RFC 3177's one-size-fits-all stance, many assign /48s to larger sites and /56s or single /64s where demand is modest.

**How many /48s are in a /32?**

65,536, which is why one ISP aggregate comfortably serves thousands of business sites.

**Should I request a /48 or a /56?**

Size for the number of /64 segments you expect to route. Both are trivially large in absolute terms; pick whichever matches your VLAN count and growth plans.

## Open this prefix in the calculator

[Open 2001:db8::/48 in the IPv6 calculator](https://itinsighthub.com/ipv6-subnet-calculator/?q=2001%3Adb8%3A%3A%2F48)

### Related IPv6 prefixes

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← IPv6 /47 prefix
IPv6 /52 prefix →

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