How can I know if my computer is behind NAT?

networking nat
JAN picture JAN · Jan 21, 2014 · Viewed 36.5k times · Source

I'm trying to understand NAT (Network Address Translation) .

Can someone explain how can I determine if my computer is using a NAT (behind a NAT) , or if it using its own IP address ?

Answer

selbie picture selbie · Jan 21, 2014

What Barmar said in the comments is the easiest way. Obtaining your IP address over HTTP is indicative that you are behind either a NAT or an HTTP Proxy server. (I suppose it's possible you could have a public IP address, but your device is configured to route HTTP over a caching proxy).

Formal NAT detection and NAT classification can be done with the STUN protocol or equivalent protocol in which a UDP or TCP service echoes back the IP address back to the client that connected to it.

Another telling sign if you are behind a NAT is that your local IP address is in a private IP address range such as the 192.168.x.y range, the 10.x.y.z range, or then 172.16.0.0-172.31.255.255 range.

And pretty much any Wi-Fi setup is going to be a NAT configuration.

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