Recently my company purchased a Polycom "RealPresence® Group 500" video conferencing system for use at 3 remote offices. A reseller installed and is configuring the system.
The 3 offices are behind Cisco 881W routers performing PAT on the LAN side.
The polycom unit is able to place calls between offices but no audio or video is displayed.
I've been reading up on the issues surrounding H.323 and NAT and am at somewhat of a loss as to how to make this work.
Cisco TAC examined the router config and we watched the NAT trans table as a call was placed. The translations appear to work fine and the several ports that the polycom negotiates are opened properly. However, no A/V.
As a test, I connected the polycom unit directly to the internet with the public IP and A/V works perfectly.
One of the solutions suggested online is to create a DMZ and place the polycom unit there with a second public IP. I'm not exactly sure how to do this.
Any help with this approach (or any other suggestions) is greatly appreciated.
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I'm wondering how does the near side "know" what IP and ports to direct to on the far side, and how does the far side know to open those ports if PAT is dynamic?
I could see this working if NAT/PAT is static, basically a DMZ like approach.
An alternative solution would be to define a site-to-site VPN tunnel and run your video conferencing through it.
As it has been over a month, I was wondering if you had got this working. It does appear that the issue you are experiencing is firewall related. Polycom have a range of signalling and media ports (different from Cisco) that will need to be opened. As I work for Interlink Vision a Polycom video and infrastructure partner and Cisco select partner I would advise you to liaise with your reseller and ask them to do there job properly. If however your reseller is not filling you with confidence please feel free to contact myself and I will put you in touch with a senior video engineer from our support team who can liaise with yourself and your firewall engineer to help resolve the issue.
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