What Is an IPv6 /48 Block? (And Why It Gives You 4,096 Addresses)

Every IPv6 proxy service advertises a "/48 block" or "4,096 addresses," and most explain neither. This is the part worth understanding, because it determines what you can actually do with the proxy and where its limits are.

IPv6 addressing in sixty seconds

An IPv6 address is 128 bits, written as eight groups of four hexadecimal digits:

Two conventions make that readable. Leading zeros inside a group can be dropped, and one run of consecutive zero groups can be collapsed to ::. The same address becomes:

The first 64 bits — 2001:19f0:6000:95e8 — are the network prefix. The last 64 bits identify the host. That split is not arbitrary; it is baked into how IPv6 subnets are designed, and it is why a single allocation can contain an enormous number of addresses.

What "/48" actually means

CIDR notation describes how many leading bits are fixed. A /48 means the first 48 bits are the network, leaving the remaining 80 bits free for addresses inside it.

That is 2^80 possible addresses — far more than any proxy service would ever use. Real-world allocations are drawn more conservatively, and a /48 is conventionally carved into 65,536 separate /64 subnets, each of which holds 2^64 addresses.

For proxy purposes the useful convention is simpler: a /48 is treated as 4,096 usable addresses. That number comes from using 12 bits of the host portion for addressing (2^12 = 4,096) while staying well clear of the subnets reserved for other purposes.

Here is the same block written three ways:

Why providers hand out /48s at all

Because the supply makes it possible. IPv4 blocks of 4,096 addresses have not been freely available for years — they trade on a secondary market at real money per address. IPv6 space is handed to hosting providers in much larger chunks, so subdividing a /48 per customer costs the provider essentially nothing.

That is the structural reason IPv6 proxy services can price per gigabyte instead of per IP. Compare:

• IPv4: the provider pays per address, so you pay per address.
• IPv6: the provider allocates from a block they already hold, so you pay for bandwidth.

If you have ever wondered why an IPv4 proxy costs $0.50–$3 per IP per month while an IPv6 pool costs a couple of dollars per terabyte, this is the answer.

How rotation works inside a /48

When your client connects to an IPv6 proxy gateway, the gateway picks a source address from your block for that request. On the next request it picks a different one. From the target's perspective, two consecutive requests came from two unrelated addresses.

Two modes are worth distinguishing:

Rotating. A new address per request. This is the default, and it is what makes 4,096 addresses useful for rate-limit avoidance.

Static (pinned). The gateway holds one address for the life of a session. Necessary for anything stateful — logging in, filling a cart, completing a multi-step form — where an address change would invalidate the session.

Good providers let you switch between the two without changing your client code, because the pinning happens at the gateway rather than in your application.

The catch: a /48 shares a reputation

Here is the part that marketing pages tend to omit.

Because all 4,096 addresses come from the same prefix, they share a neighbourhood. Some anti-bot systems do not evaluate single addresses — they evaluate prefixes, ASNs, or whole ranges. If your /48 gets flagged, you do not lose one address; you lose all 4,096 at once.

This is different from the IPv4 failure mode, where a burned IP is a burned IP and the others in your pool are unaffected.

In practice:

• Against per-IP rate limits, a /48 is close to ideal. Each address gets its own budget.
• Against prefix-level filtering, a /48 behaves like a single identity. Rotation does not help.
• Against reputation systems, datacenter prefixes start behind, regardless of protocol.

Rotation solves throughput problems. It does not solve trust problems.

What to check before buying

Does the service give you the whole /48, or share one? "Up to 4,096 IPs" is not the same as "a dedicated /48." Shared blocks mean other customers' behaviour affects your reputation.

Is rotation per request or per session? Both are useful, but you want the choice, and you want to control it without redeploying your client.

Can you pin an address? If sticky sessions cost extra or are unavailable, stateful automation becomes painful.

Is it priced per GB? Per-IP pricing on an IPv6 pool usually means you are paying for scarcity that does not exist.

Do you get HTTP and SOCKS5? HTTP covers web scraping. SOCKS5 covers everything else — SSH, RDP, databases — through the same credentials.

Seeing it for yourself

The IPv6 proxy network page lists per-region pools and pricing, and the code samples there show the connection strings for cURL, Python and Node.js. Since rotation happens at the gateway, adopting it is usually a one-line change: point your existing HTTP or SOCKS5 client at the proxy and let the block do the work.