CGNAT Check
See whether the address this site received is in CGNAT shared space (100.64.0.0/10), an RFC1918 private range, another reserved range, or a public address. Then compare it with the WAN IP on your router.
What the comparison means
- WAN in 100.64.0.0/10: CGNAT is likely on a single home router. The public address on this page, when it differs, is the upstream exit.
- WAN private or otherwise reserved, and different from a public address here: another NAT sits in front of the router. That can be the ISP or a second router at home.
- WAN and this page show the same public IPv4: the router holds the address sites see, so CGNAT is less likely. The address can still change, and inbound ports can still fail.
- A normal public address on this page, before you compare, does not prove the address is yours alone.
Turn a VPN off before comparing, or this site sees the VPN exit. This page does not show a yes/no CGNAT badge.
What is CGNAT? explains shared public IPv4.
How to tell if you're behind CGNAT walks through the same WAN comparison, including double NAT.
Frequently Asked Questions
Does this page prove I am behind CGNAT?
No. It classifies the address this site sees, and a WAN address you paste, as shared CGNAT space, RFC1918 private, another reserved range, or public. A normal public address here can still be an ISP exit shared by many customers. Compare it with the WAN IP on your router, rule out a second home router, and ask the ISP when inbound access matters.
What does 100.64.0.0/10 mean?
That block is Shared Address Space (RFC 6598), used for carrier-grade NAT. It is not a globally routable public address and it is not an RFC1918 private range such as 192.168.x.x. If your router WAN address is inside 100.64.0.0–100.127.255.255, CGNAT is likely on a single-router setup.
Why can the website IP and the router WAN differ?
This site sees the address after upstream NAT. The router WAN address is what your home gateway holds toward the ISP. If WAN is shared space or private and this site shows a different public address, another NAT sits in front of the router. That can be ISP CGNAT or a second router at home.