What is CGNAT and why do providers use it?
CGNAT (Carrier-Grade NAT) is a large-scale address translation method providers use to let many subscribers share one public IPv4 address and conserve a scarce resource. With CGNAT, your router WAN IP may show an address in the 100.64.0.0/10 range instead of a real public IP.
Last updated
Why does CGNAT exist?
There are only about 4.3 billion IPv4 addresses worldwide, far fewer than the number of internet-connected devices today. CGNAT emerged because providers can no longer give every subscriber a public IP of their own.
Just as a home router uses NAT to share one public IP among devices at home, CGNAT lets a provider share one public IP among many subscribers, one layer further out.
How do I tell if my connection uses CGNAT?
Check the WAN IP in your router admin page. If it starts with 100.64., your connection uses CGNAT, since that range is reserved specifically for it and is not a real public IP.
If your router WAN IP differs from the public IP shown on ipnow.kr, a CGNAT device at your provider is translating the address once more in between.
What problems can CGNAT cause?
If you want to run a home server or use port forwarding to reach a camera or NAS from outside, CGNAT can break it, since the router WAN IP is not a true public IP.
Asking your provider whether a static public IP add-on is available is the usual fix. See dynamic vs static IP for related background.
- 100.64.0.0/10: the range reserved for CGNAT
- A router WAN IP in this range means CGNAT is active
- Port forwarding and self-hosted servers work better with a real public IP
Is CGNAT the same thing as a private IP?
They are similar but different. A private IP, such as 192.168.x.x, is managed by your own home router, while a CGNAT range (100.64.x.x) is used by the provider to group many subscribers together. See public vs private IP for the full comparison.
| Item | Value | Source |
|---|---|---|
| CGNAT shared address range | 100.64.0.0/10 | RFC 6598 · 2012-04 |
Frequently asked questions
Do all providers use CGNAT?
It depends on the provider, the plan, wired versus mobile, and the region. Checking your router WAN IP or asking your provider directly is the most reliable way to know.
Can I ask to opt out of CGNAT?
Some providers offer a separate plan or add-on with a static public IP. The exact process depends on your specific provider.
Does CGNAT cause problems for normal browsing?
General use such as browsing and streaming is usually unaffected. The impact mainly falls on servers and port forwarding that need an inbound connection to your network.
Does IPv6 help avoid CGNAT?
IPv6 has a much larger address space, so devices can often get a unique address without CGNAT, though actual IPv6 support still depends on your provider and the service you are reaching.