Here are two great free tools to help with setting up VoIP or SIP or having problems on the network:

https://www.voiptroubleshooter.com/diagnosis/index.html

https://www.ethereal.com/

I checked into commercially available software based VOIP tools and found that most cost about $4000.00. That's a lot to spend at this point. When you guy's get a chance, come back and give feedback on these free ones for the rest of us.

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Have used Ethereal to determine addresses when our IP-SLA decided to pick its own address and we needed to find its real address to change it.
We have also used www.packetyzer.com and it works great.