Does port 19302 for Google’s STUN need to be open?

Yes and No.

• Yes, 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
  
  
• No, port 19302 is not required for WebRTC clients. Each WebRTC client requires a STUN response and will attempt to use Genesys Cloud STUN (UDP/3478) and Google STUN (UDP/19302) in parallel to determine its own external IP address. Only one successful response from either service is required. If port 19302 is not open, WebRTC clients can still succeed with STUN response from the Genesys Cloud STUN servers. Although the port 19302 is optional, there is no way to disable the requests.

For more information, see About ports and services for your firewall.