VICIPanel
Troubleshooting/One-way audio on connected calls
CriticalNetwork

One-way audio on connected calls

Agents can hear callers but callers can't hear agents, or vice versa.

Symptoms

  • •Caller says 'hello hello' but agent gets no response when speaking
  • •Agent hears caller fine but caller reports total silence
  • •One-way condition persists across multiple calls and agents

Common causes

  • •NAT traversal misconfigured, RTP packets not reaching one direction
  • •Firewall blocking UDP port range (typically 10000-20000)
  • •Codec mismatch between SIP trunk and agent phone
  • •STUN / ICE not configured for WebRTC agents
  • •Asymmetric routing: inbound and outbound go different paths

How to fix it

  1. 1
    Verify RTP port range open in firewall both directions (UDP 10000-20000 default)
  2. 2
    In `rtp.conf` ensure `rtpstart` and `rtpend` match firewall rules
  3. 3
    Check `sip.conf` has `externip` and `localnet` set correctly for NAT
  4. 4
    For WebRTC: confirm STUN server reachable from agent's network
  5. 5
    Run `sip show channels` during a call to see negotiated codec
Network health and operational view in VICIPanel
How VICIPanel helps

VICIPanel's call audit view shows the negotiated codec, RTP path health, and STUN-related stats per call leg so one-way audio is diagnosable in seconds, not hours.

Related issues

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Agent's browser-based softphone fails to establish audio path.

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