Yes, STUN is available and used by the WebRTC phones, but not private STUN - only Genesys and Google. Here is a nice diagram: Detailed WebRTC diagram - Genesys Cloud Resource Center (mypurecloud.com) and here is another good one: WebRTC call flow - Genesys Cloud Resource Center (mypurecloud.com). Are you using local edges or cloud?
As for Edge devices, Genesys recommends that port 19302 be open for Edges using WebRTC; however, it is not required. Edges use port 19302 to access Google's STUN servers to get external IP addresses. In some rare circumstances, using the public Google STUN service helps establish calls more quickly. If port 19302 is not open, Genesys Cloud will use Genesys Cloud STUN and TURN services in AWS via port 3478
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Robert Wakefield-Carl
ttec Digital
Sr. Director - Innovation Architects
Robert.WC@ttecdigital.comhttps://www.ttecDigital.comhttps://RobertWC.Blogspot.com------------------------------