Software⏱️ 3 min read📅 2026-06-19

How to Fix: Asterisk: chan_sip.c:4321 __sip_reliable_xmit: Serious Network Trouble; __sip_xmit returns error for pkt data

Asterisk PBX issue with SIP transmission error.

Quick Answer: Check the SIP configuration and ensure that the Grandstream HT813 gateway is properly configured to handle SIP traffic.

Asterisk is experiencing a serious network trouble issue, causing unreliable SIP transmissions to the Grandstream HT813 gateway. This problem affects users who dial out from IP phones connected to the Raspberry Pi-based Asterisk PBX.

This frustrating error prevents effective communication between the IP phone and the PSTN, leading to failed calls and disrupted connectivity.

💡 Why You Are Getting This Error

  • The primary reason for this issue lies in the configuration of the Grandstream HT813 gateway. The incorrect use of insecure=port parameter in the sip.conf file may cause SIP transmissions to fail.
  • An alternative explanation is that the Asterisk PBX is not configured properly to handle the specific needs of the Grandstream HT813 gateway, leading to unreliable SIP transmissions.

🚀 How to Resolve This Issue

Reconfigure the Grandstream HT813 gateway and adjust the sip.conf file

  1. Step 1: Log in to the Grandstream HT813 gateway's web interface and navigate to the 'Advanced Configuration' section. Ensure that the 'Insecure Port' parameter is set to a value other than port.
  2. Step 2: Restart the Grandstream HT813 gateway after making these changes. This will ensure that any cached configuration information is discarded, allowing Asterisk to re-establish a stable connection.
  3. Step 3: After restarting the gateway, return to the sip.conf file and update the insecure=port parameter to match the new setting on the Gateway. Save the changes and restart the Asterisk service.

Reconfigure the Asterisk PBX to handle Grandstream HT813 gateway requirements

  1. Step 1: Log in to the Asterisk web interface and navigate to the 'Advanced Configuration' section. Ensure that the 'DTMF Mode' parameter is set to 'rfc2833', which is compatible with the Grandstream HT813 gateway.
  2. Step 2: Adjust the 'Can Reinvite' parameter to match the specific requirements of the Grandstream HT813 gateway, if necessary.

🎯 Final Words

By following these steps, you should be able to resolve the SIP transmission issue and establish a stable connection between your Asterisk PBX and the Grandstream HT813 gateway. If issues persist, further troubleshooting may be required to identify any underlying configuration or hardware problems.

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