What Is CGNAT, and Does It Affect You?
CGNAT, short for Carrier-Grade NAT, is a way for internet providers to stretch their limited supply of IPv4 addresses by sharing a single public address across many customers at once.
Most of the time you'd never know. It only shows up when you try to do something that needs the outside world to reach you directly.
Why ISPs use it
There aren't enough IPv4 addresses to give every customer their own. CGNAT puts many households behind one shared public IP, with the carrier juggling the connections behind the scenes. It's cheaper than buying more addresses and buys time until IPv6 is everywhere.
What it affects
- Port forwarding stops working, because you don't control the shared public IP.
- Hosting a game or server for others to connect to becomes difficult.
- Some peer-to-peer apps and remote access tools struggle.
- Online gaming may show a strict or moderate NAT type.
How to tell if you're behind CGNAT
Compare the public IP shown on this site with the WAN IP listed in your router's settings. If they're different, and the router's WAN address is in a shared range like 100.64.x.x, you're almost certainly behind CGNAT.
What you can do
- Ask your ISP for a public or static IPv4 address, which usually sidesteps CGNAT.
- Use IPv6 if your ISP and the service support it, since CGNAT is an IPv4 workaround.
- For remote access, use a relay or tunnelling service that doesn't need incoming ports.