said by Mango:Is there an easy way to test what type of NAT a router uses?
Here are a few that I know about.
* NAT tester at »
nattest.net.in.tum.deRequires Java, unfortunately. I've found that the final test (UDP Reverse Traceroute) can hang. If it does, then you can abandon it and still see the results of the other tests by clicking on the "permanent link for your results" link. It also tests for the presence of SIP and FTP ALGs. For my router, it reports the correct results for the things that I know about by other means.
* On Mac OS X, launch the Messages application. Skip the setup if you're not a chatter. From the menu bar, go to Video > Connection Doctor. Choose "Network Status". "Router Type" should show the NAT type. I've found that sometimes it fails to detect the type the first time; toggling to "Statistics" and back to "Router Type" seems to fix this. It reports the correct NAT type for my router.
* I no longer have one of these ATAs, but I've used this before with success. Sipura/Linksys ATAs have a "STUN Test Enable" option (with the other "NAT Support" options) which, when set "on" and with STUN configured, will report the detected NAT type in the debug log on a coldstart of the device.