troubleshooting Question

Cisco 79XX phones unable to see XML data over a SonicWALL VPN

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bodineperry asked on
RoutersHardware FirewallsNetwork Operations
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Hi everyone,

I'm having a bit of a hard time with my new SonicWALL TZ 100 that I installed at our corporate office.  We use Cisco 7940 and 7960 SIP phones at all of our offices.  The phones connect to our main PBX (trixbox) at the corporate office via IPSEC site-to-site VPNs.  All calls are getting through and working properly, but ever since the SonicWALL installation, all phones at remote locations are no longer able to properly view the phone directory.  The phone directory is located at http://192.168.1.xxx/directory.  Phones on the local network are able to view the XML directory just fine, but the remote phones are getting a "BTXML error - XML Parse Error."  The remote phones are also no longer receiving the corporate logo on their screens upon bootup, which is located at http://192.168.1.xxx/cisco/logo.bmp.

This worked just fine with our previous router, which was a Linksys RV082.  I've been experimenting with several SonicWALL settings, created allow-all policies, and even disabled IDS temporarily to no avail.  I've read that sometimes phones would get this error if they were sitting behind a NAT and connecting to the WAN port of the PBX, and that designating the phone as DMZ would resolve it, but since we're on a VPN with all traffic allowed both ways, I can't see why the ports are not communicating properly.  

If I repeatedly try to display the directory several times, I will sometimes get the initial page of the directory, but going any further from there invariably gives me another BTXML error.

Any ideas?  Am I missing something, or is this kind of network behavior between SonicWALL and Cisco's phones a common occurrence?  Any light shed on this would be greatly appreciated!

UPDATE:  Inspecting the access_log and error_log on the trixbox shows no activity whatsoever when a BTXML error is displayed on the phones.  When I do make it through for a successful connection, access_log shows this:

192.168.25.xxx - - [10/Aug/2011:22:50:02 -0400] "GET /directory/PhoneUI/index.php?name=SEPXXXXXXXXXXXX HTTP/1.1" 200 4763 "-" "Allegro-Software-WebClient/3.10b1"
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