Is STUN server necessary in FreePBX

This is a simple question as I’m just trying to confirm what I believe. When FreePBX:

  • Sits behind NAT with a static public IP
  • The “External Address” has been set to the public static IP

then a STUN server should not be required?

Recently the ISP developed a routing problem which made much of Google unreachable, among other things, but should not have affected voice in any way. Yet, the SIP provider was reporting FreePBX unreachable and callers would get a busy, while FreePBX would actually ring the phones about 15 seconds later… was very strange.

It turned out I had entered a Google STUN server, Google was unreachable, and the call out to it was taking 3 seconds to time out. The SIP provider wasn’t willing to wait 3 seconds for a response, so tried the invite 3 times and then gave up. FreePBX, on the other hand, saw the 3 invites, made 3 calls to the STUN server, replied to the SIP provider, who by then was long gone, and then finally rang the phones, only to die when the RTP could not be negotiated.

It was easily remediated at the time by changing to a reachable STUN server, but it occurs to me that it’s probably completely unnecessary and represents a vulnerability that can be completely eliminated. I just wanted to be sure.


As you have an external static IP, you don’t need to configure a STUN server on FreePBX SIP settings.

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