Assumptions When Resolving An Issue

I help out a lot across various avenues: mailing lists, forums, issue tracker, IRC, and more. I’ve noticed a trend recently where people aren’t verifying any of the assumptions they have about their problem or situation. I thought I would take a blog post to reiterate how important it is to verify your assumptions. It can save you, and anyone helping you, an enormous amount of time as your issue may actually be caused by an assumption that is then proven false. Break down your problem into parts and verify each. To help here are some common things to look at:

  1. Verify that traffic is reaching Asterisk through the use of “pjsip set logger on”. If you don’t see the traffic then go a level above and verify that it is not getting blocked by a firewall. If you see traffic in tcpdump but not in Asterisk, then you have a local firewall on the system blocking it. The tcpdump or wireshark utility captures traffic BEFORE a firewall blocks it.
  2. If behind NAT verify that your PJSIP transport is configured with the correct external IP address and correct local network information.
  3. Verify your endpoint configuration is as you would expect.
  4. Verify that the correct endpoint is being used for incoming PJSIP traffic by looking at the logs.
  5. Verify your dialplan using the “dialplan show” CLI command.

While these are only a few, I’ve found that a lot of issues can be resolved just by looking at these.

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