Calls that disconnect after approximately 30 seconds are often associated with NAT traversal issues, SIP ALG, or incorrect SIP port settings. Enabling NAT Keep Alive and disabling SIP ALG can help resolve the problem.

NAT Keep Alive is a feature that maintains an active connection between the VoIP device and the SIP server, preventing the router or firewall from terminating the communication.

SIP ALG (Session Initiation Protocol Application Layer Gateway) is a feature found in many routers that attempts to manage SIP traffic. However, it often causes issues such as dropped calls, audio loss, or SIP registration failures.

Yes. NAT settings, firewall rules, or SIP ALG functionality on the router can affect the proper operation of VoIP services and lead to call disconnections.

The most common symptoms include:

• Calls that disconnect unexpectedly

• No audio during calls

• One-way audio

• SIP registration failures

• Problems with incoming or outgoing calls

Does changing the SIP port affect my phone number?

No. Changing the local SIP port only affects how the device communicates with the SIP server. It does not change your phone number or any of your telephony services.