# 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. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.anyone.io/relay/troubleshooting/reachability.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.