Call connects but no media

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Call connects but no media

Problem Summary Cisco remote expert is installed & Configured. Consumer complains that they can make a call but there is no audio or video
Error Message No specific error message for this issue.
Possible Cause This issue is generally due to clients having problems setting up the media path to the media broker
Recommended Action

Please check following:

  • Media Broker configuration:  Check the WebRTC Client configuration of the media broker in the Web Admin:
  1. If no Media Broker is configured the call will not set up.
  2. Does the external address match the external interface for the media broker?
  3. Does the internal address also match the internal interface?  Please see Understanding MediaBroker Ports for more information.
  • A firewall is blocking the media path: Verify that the firewall is configured to forward from WebRTC public Address/port to local Address/port.The WebRTC public port (defaults to 16000) is not open on all firewalls between client and media broker.You can check this externally from a simple port checker like https://pentest-tools.com/discovery-probing /udp-port-scanner-online-nmap
  • A VPN is blocking the media path: Some VPNs may not be configured to allow 2 way UDP. Clients connecting via VPN may experience no Voice and Video. An indication of this problem may be seen in the media broker proxy.log with the following error message repeatedly output.

ERROR com.alicecallsbob.porth.rtp.proxy.routing.ProxyConnection - can't processOutgoingPacket for RTCP because remote is null

A PCAP trace may also show no STUN responses to incoming STUN requests from a client connecting via a VPN.

Reas no stun response.png

  • Multiple media broker instances are running: It is possible that 2 instances of media broker process are running and this has caused issues with the media. When this occurs you will see STUN Binding Requests in a packet capture, but the Media Broker will not be processing the STUN Binding Requests. To check for this run 

ps -eaf | grep [r]tp-proxy   

   and ensure only one process is running. If not stop or kill the both processes and restart media broker.

service media_broker start

Release Remote Expert Mobile
Associated CDETS # None


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