Most common reason for call drops at 30 sec in a VoIP call lies in the network router or firewall. Below is a brief checklist of common causes of malfunctioning:
- Most issues are caused by the router having multiple IP addresses and the service provider sending a reply to the wrong IP address.
- Check that the router/firewall is blocking SIP traffic – you must make sure that the router allows VoIP traffic. With some routers you need to disable the SIP/ALG field to allow VoIP traffic.
- Check also that the right IP address has been entered for mapping the router i.e. the router is not programmed correctly to send the VoIP traffic to the PBX and is sending the VoIP traffic to the wrong machine.
The best way is to restart the router or firewall. Following articles will help you understand the issue and resolve -
- https://stackoverflow.com/questions/27614532/sip-call-drop-after-30seconds
- https://voipstudio.com/blog/causes-and-solutions-to-voip-call-drops/
- Video: https://www.youtube.com/watch?v=UIInnaDC7tM