# CGNAT & IPv4 reachability

### What is CGNAT?

Carrier-Grade Network Address Translation (CGNAT) is a technique used by Internet Service Providers (ISPs) to deal with the shortage of available IPv4 addresses. In a CGNAT environment, multiple customers share a single public IPv4 address, hindering the ability to directly forward ports to devices within a network.

### Diagnosing CGNAT

#### **Check Your Router's WAN IP:**

* Log in to your router and locate the **WAN IP** address. If it's a private IP address (e.g., 10.x.x.x, 100.x.x.x, 192.168.x.x,), your network is likely behind a CGNAT.
* Check if your routers **WAN IP** matches the **IP address** on [browserleaks.com/ip](https://browserleaks.com/ip), if the IP's does not match then you can be certain CGNat is enabled for your Internet service.

**Check with Your ISP:**

* Contact your Internet Service Provider and inquire about your IP address type. If they confirm it's a private IP, you're likely under CGNAT.

### Dealing with CGNAT

**Contacting Your ISP Requesting a Dynamic Public IP:**

* Inform your ISP about the port forwarding needs.
* Request a dynamic public IP address to enable you to forward ports.
* Some ISP's charge extra for a static IP if the ISP can't help you with a dynamic IP.