If the 3CX Firewall Checker shows green but there are audio issues, what could be a potential culprit?

If the 3CX Firewall Checker indicates a green status, it signifies that the firewall is properly configured to allow the necessary traffic for 3CX operations. However, even with a correctly configured firewall, audio issues can still occur, often due to specific factors affecting communication.

SIP ALG (Session Initiation Protocol Application Layer Gateway) is known to interfere with VoIP systems by altering SIP packets, which can lead to problems such as one-way audio or dropped calls. While the firewall setup may correctly allow data to pass through, SIP ALG can modify or block the SIP packets that are crucial for establishing VoIP communications effectively. Disabling SIP ALG on the router or firewall is frequently recommended to resolve these audio issues.

Other options such as firewall settings and wrong extension credentials would typically lead to broader connectivity issues rather than just audio problems, while network bandwidth can impact call quality but doesn't directly implicate a correctly configured firewall. Therefore, recognizing SIP ALG as a potential culprit provides an important insight into troubleshooting audio issues in a situation where the firewall check is successful.