MXIE Soft Phone has one way audio

Soft phone users connecting over a SonicWall SSL vpn have one way audio (the user can hear the person they call, but the receiving caller cannot hear them). Zultys tech support was not helpful.
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BWaringConnect With a Mentor Commented:
If they are connecting through the SW SSL VPN, then fw or NAT shouldn't affect the connection, since the softphone traffic should be all in the VPN tunnel.

Some ideas for testing... Can you try this locally on-site, without the VPN to confirm it works properly? That would at least rule out most issues on the local machine. If that works, then try bringing up the VPN locally, as that would help rule out the VPN (not completely, but somewhat).

Are there any routes needed in the SW or other local device to direct the voice traffic back through the VPN?

And yes, it definitely could be a QoS issue. If you could connect the client locally on the WAN side of the SW and bring up the VPN that should let you know if it works from the WAN side.  
jfaubiontxConnect With a Mentor Commented:
Check the soft client to see what RTP port it is using and then make sure that port is open in the firewall. I can't remember what port the MXIE used but it was different that what we expected. In our original testing we opened UDP1024 to UDP65535 until we found the port. Unfortunately I no longer have access to that customers firewall or I'd look it up. I seem to remember that we had opened 10000-20000 and it was using something in the 40000-42000 range. Don't quote me though as it's been a while.
explorer648Author Commented:
Thanks for the info, jfaubiontx. I should add that sometimes the calls actually do work, but the sound quality is horrible. Do you think that the issue might be related to NAT traversal? I'm thinking it is more of a QoS issue. Thoughts?
jfaubiontxConnect With a Mentor Commented:
Doh! I didn't notice the VPN part of your question. If connecting through VPN, NAT is not an issue. It certainly acts like a bandwidth issue. Can you run an MTR across the VPN to see if there are packet loss issues?
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