There are two methods that can be used to help debug VoIP issues. These are:

1. Capture VoIP debug logs

  1. Telnet to the router
  2. Enter the command “voip debug flush” to clear all current logs before making a phone call.
  3. Enter the command “voip debug show” to display the log after the phone call has ended.

If there are several sip accounts configured in the router, there may be many periodic useless logs (such as refreshing register status), which may make it difficult to check the logs. So it is a good habit to flush logs before duplicating the issue.

Note: The default telnet application that is available in windows has row display limitations. This may result in some of the logs scrolling of the screen.

2. Capture Wireshark packets

Use softphone (x-lite, sjphone and etc) to register and make a phone call. Use wireshark to capture the softphone packets

You will notice the message body is almost the same as that in the telnet VoIP debug logs.