IP

CGNAT Check

Best-effort CGNAT checks

Explainer

What is CGNAT?

Carrier-grade NAT lets an ISP share limited public IPv4 addresses across many customers. That makes address management easier for the ISP, but it can complicate inbound connections.

Why ISPs use it

Public IPv4 space is limited. CGNAT lets an ISP keep offering IPv4 connectivity even when unique public addresses are scarce or expensive to assign one by one.

Why it can cause confusion

If your router WAN IP is private, shared, or otherwise non-public, your router may not be the real edge device on the public internet. Inbound traffic can stop before it ever reaches your own port forwarding rules.

What this usually affects

Self-hosting, remote desktop, game servers, camera access, and some peer-to-peer apps can all be harder to run when inbound IPv4 connections never reach your home network.

If you want a practical next step, use the CGNAT checker and then verify the result with your router status page and your ISP.

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