The Address Space Problem
IPv4 provides about 4.3 billion unique addresses. With billions of connected devices worldwide, those addresses ran out. ISPs responded by putting multiple customers behind a single shared public IPv4 address through a technique called Carrier-Grade NAT (CGNAT). IPv6 solves this by using 128-bit addresses—enough for every device on earth to have a globally unique address many times over.
How Dual-Stack Works
Most ISPs and devices now operate in dual-stack mode: they support both IPv4 and IPv6 simultaneously. When you visit a website, your device checks whether the destination has an IPv6 address. If it does, your device uses IPv6. If not, it falls back to IPv4. This happens transparently—you do not need to configure anything or choose between them.
When IPv6 Affects Your Experience
| Scenario | IPv4 Behavior | IPv6 Behavior |
|---|---|---|
| Standard browsing | Works fine | Slightly lower latency to IPv6 sites |
| Behind CGNAT | Incoming connections blocked, gaming issues | Direct public address, no CGNAT |
| Port forwarding | Often impossible behind CGNAT | Works natively |
| P2P / gaming / VoIP | Can be unreliable behind CGNAT | More reliable direct connections |
CGNAT: The Real IPv4 Problem for Home Users
If you are on a mobile broadband or cable plan, you may be behind CGNAT without knowing it. Signs include being unable to host game servers, port forwarding not working despite correct router settings, and some VoIP apps failing to connect. Running a CGNAT check (your public IP from a speed test vs. your router's WAN IP) reveals whether this applies to you. IPv6 bypasses CGNAT entirely because each device gets its own global address.
Does IPv6 Make Speed Tests Faster?
Not significantly for most users. The theoretical benefit of IPv6 is reduced NAT overhead and potentially more direct routing. In practice, you might see 1–10ms lower latency to IPv6-native servers. The more meaningful benefit is for CGNAT users, where switching to IPv6 for P2P and gaming applications removes connection reliability problems that look like speed issues.
Frequently Asked Questions
What is the difference between IPv4 and IPv6?
IPv4 uses 32-bit addresses—about 4 billion total, now exhausted. IPv6 uses 128-bit addresses with virtually unlimited space. IPv6 also eliminates NAT for most connections.
Is IPv6 faster than IPv4?
Marginally for most users—1–10ms lower latency to IPv6 sites. The bigger benefit is for CGNAT users, where IPv6 eliminates connection reliability problems.
What is CGNAT and does it affect me?
CGNAT shares one public IPv4 address across multiple customers. It blocks incoming connections and breaks port forwarding. IPv6 gives each device a public address, solving these issues.