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Last update: 2021-10-28

The phone rings, but there's no audio if you're using VPN or the Sophos Connect client

Condition

You're able to place a call and the receiving phone rings, but you don't hear any audio.

Cause

This condition occurs if the caller can't send data at the RTP stage of a SIP connection. Here's an example of this condition where Alice is the caller and Boris is the recipient.

Diagram showing SIP communication

Remedy

  1. Go to Rules and policies > Firewall rules.
  2. Make sure you've configured a firewall rule for SIP.
  3. Make sure you select the recipient's network in Destination networks. If you want to call any phone, set the recipient's network to Any.
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