CGNAT tools and guides
Find strong CGNAT signs before you keep chasing broken port forwarding
Run a best-effort IP comparison, learn what CGNAT means, and work through practical next steps if your router WAN IP does not behave like a normal public IPv4 address.
Core guide
Run the CGNAT checker
Compare your router WAN IP with your detected public IP and get a plain-English result.
Read moreCore guide
Learn what CGNAT means
Understand why ISPs share IPv4 addresses and how that affects home networking.
Read moreCore guide
See why port forwarding fails
Work through the most common reasons ports stay closed, even after router changes.
Read moreCore guide
Find your router WAN IP
Locate the internet-facing address shown by your router before you compare it.
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How the checker helps
Detect your public IP
The checker reads the IP visible to the server through forwarded headers.
Compare the router WAN IP
You manually enter the WAN IPv4 shown by your router or gateway status page.
Interpret the mismatch
Private, shared, or reserved WAN ranges often suggest another NAT layer upstream.
Quick answers
Common CGNAT questions
What does CGNAT mean?
CGNAT stands for Carrier-Grade Network Address Translation. It lets an ISP place many customers behind shared public IPv4 addresses instead of assigning a unique public IPv4 address to each customer.
Can this checker prove that I am behind CGNAT?
No. This is a best-effort browser check. It can highlight strong signs of CGNAT, but it cannot confirm every network layout or ISP setup from the browser alone.
Why does a private WAN IP matter?
If your router shows a private or shared CGNAT address on its WAN or internet page, that usually means another layer of NAT exists upstream. In many cases that prevents direct inbound connections and port forwarding from working as expected.
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