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Community Member

SPA525G Remote VPN Phone - Works for a bit then 1 way audio

We have a couple of different customers using SPA525G phones remotely using the built-in SSL VPN.  The sites where the phones are behind a Sonicwall seem to have a problem with the phones going to 1 way audio after a random number of minutes.  We can take these phones back to our shop behind a Fortigate and we do not have a problem.

Here is the topology:

525 -> Sonicwall -> internet -> UC500

Has anyone seen this before?


Anyone have an idea?

3 REPLIES

Re: SPA525G Remote VPN Phone - Works for a bit then 1 way audio

It sounds like the Sonicwall is cutting off the RTP stream.  I don't work with the Sonicwall, but if it has some kind of packet capture, or logging of blocked packets, I would try to test the call and see when it is blocking the stream.  I know many firewalls have stateful inspection to keep connections open like that, so it could be as simple as adjusting something with that.

That being said, all I can tell you is generic things to check since I don't work for Sonicwall

Community Member

Re: SPA525G Remote VPN Phone - Works for a bit then 1 way audio

Jason,

It seems like regardless of the VoIP system in question a lot of people have experienced issues with getting the Sonicwall appliances to play nice.  Some of the stuff I've read suggests doing the following:

Turning off SIP ALG or SIP Fixup or SIP Transformation is a good first step.

Past that, you'll probably have to capture network traffic to see where the RTP is getting stuck.

You can see what port is being used for audio by looking at the UDP port 5060 traffic. The RTP traffic will typically be in the UDP port range 10000-20000.

Make sure you have UDP ports 5060 and 10000-20000 open before testing.

Brent Hooper

Technical Enablement Engineer - Chicago Region

bhooper@ciscosmallbiz.com

Cisco Employee

Re: SPA525G Remote VPN Phone - Works for a bit then 1 way audio

Jason,

What firmware version is running on the SPA525G phone?

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