voip - one way audio on Vertical Communications Wave IP

I'm using a SIP trunk from Broadview with a phone system from a company called Vertical Communication. Their solution is called Wave IP. Since install we've been dealing with a random problem involving one-way audio. It is always the same, the audio goes outbound but there is no audio inbound.

Some days we have 0-1 problems and other days i feel about 5-10%+ of the calls have this problem. We've had other issues but have worked though them. This one remains.

 I'm doing wireshark captures looking at the SIP and RTP traffic. The wireshark is a mirror of all data coming in/out of the router going to the ISP SBC site. The IPs, Ports, and overall call look identical besides timestamp and ports when i compare good to bad calls. Sometimes this happens so much it is easy for me to replicate with a few test calls.

Does anyone have any suggestions for troubleshooting?  I feel i need to learn something more myself.  I've been working with Vertical and the SIP provider Broadview.
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José MéndezCommented:
You are on the right track looking at packet captures to analyze the SIP and RTP signaling. What you probably won't see in a capture, is what happens with the inbound audio once it enters into the SBC. Is it routing incorrectly? Is it routing to another network endpoint (firewall, router, switch) that actually drops the packet?

That part you'll have to find out with more captures until you narrow down to hopefully 1 or maybe more devices where in different tests, RTP traffic is missing. So basically, you have to go port by port checking where is the audio being dropped in the inbound direction. If you can see audio arriving from the provider into the SBC, the next question is: can you see it getting routed out through another interface? And if so, can you see it reaching the next network card?

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First LastAuthor Commented:
Correct answer. You cant do a capture in one or two locations then expect to find the problem. We had to go port by port, then found the problem. Thank you.
José MéndezCommented:
Glad it helped a bit.
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