Question

Trying to get NAT working on a Polycom 330 phone using the 3cx phone software.

Asked by: colonialiu20

Here is the scenario. We have a 3cx server which is at our main office behind NAT. We are looking to deploy VOIP phones in district classroom sites which will be behind other school district NATs. We have purchased a Polycom Ip 330 phone and have it set up and working perfectly on our internal system with the 3cx server.

When we place one of these in an external classroom site I am able to call out from the phone and connect and talk no problem. When I have someone call the phones extension on the 3cx system it rings the phoen at teh external classroom site but it will not allow me to pick up the call and answer it. I am assuming this is because of the NAT translation at the external classrooms.

Trying to research this I see we can use a stun server to help NAT translation, but the issue is Polycom of course doesn't support STUN. I'm glad they made this easy!!!! So contacting Polycom's support they just directed me to the manual which has a few things regarding NAT and not much help at all.

What suggestion could be made for my scenario? Since the SIP connection works but the RTP voice connection seems to have issues when traveling through a NAT and then having to travel through another Nat to hit the phone server. Has anyone ecountered this scenario using Polycom VOIP phones? Would it be better to purchase a SNOM phone that lets us use STUN server settings to help translate both NATS? Any suggestions or help would be appreciated because Polycom wasn't much help at all.

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Asked On
2009-06-26 at 06:55:40ID24525112
Tags

VOIP

,

NAT

,

Polycom 330

,

3cx

Topics

Voice Over IP

,

Telecommunications

,

IP Telephony

Participating Experts
3
Points
500
Comments
4

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Answers

 

by: koszegiPosted on 2009-06-26 at 12:40:55ID: 24724119

Either you will have to get a phone that support stun or open the ports on the NAT devices needed for the RTP voice/media stream (Port forward).

good luck.

 

by: colonialiu20Posted on 2009-07-01 at 09:09:07ID: 24755788

Does anyone know if there is a way to set a Polycom VOIP 330 phone to send traffic over a specific range of ports for RTP? There are settings in the web interface for RTP and NAT, but the documentation for these phones all point to configuration files sent to the phones by provisioning servers which we aren't planning to use. We are setting this phone up manually on the web configuration pages. Has anyone got this working on a Polycom Ip 330 phone? We are planning to buy other Ip phones in the future since this is such a hassle with polycom phones, but currently this is the phone we bought.

 

by: cjwhelan3Posted on 2009-07-15 at 23:51:24ID: 24866917

I have a similar situation:  A 3CX server at our "main office" behind a firewall, and then a number of Polycom phones (in our case, the IP 430) distributed at a number of remote locations, each behind their own firewalls.  What is clear is that if these Polycom phones supported STUN, this would be way easy, and you could (essentially) just plug in these phones behind these remote firewalls and they'd "just work" (of course after making the obvious settings like the location of your 3CX server).  But alas, STUN just does not seem to be an option for Polycom phones.

The solution that has worked great for me is to get fixed/static IP addresses for these remote locations.  Generally that has been about $5 month extra per location, which kind of sucks on the one hand, but isn't that much of a burden on the other.  Then in the phone's configuration, in the "IP Address" field in the "Network Address Translation" section, you enter this static, public IP address (of the firewall that the phone is behind).  You then need to configure your firewall to port-forward the control and RTP ports to the phone (which also means giving your phone a fixed "internal" to the firewall IP address).  Typically for the 3CX system that would be ports 5060 and 9000 through 9049.

In short, think of if you were putting a web server behind this remote firewall; you'd want your firewall to have a fixed IP address, and then you'd configure it to port forward port 80 to the fixed, internal IP address of your webserver behind the firewall.

Again, it works great for me, albeit, it is a more involved configuration and you need fixed IP addresses at your remote locations.

 

by: IDEASITPosted on 2009-07-24 at 11:06:13ID: 24937399

To resolve this problem you need to make sure that the NAT firewall you are using is SIP aware.  Most of the brand name firewalls have SIP ALG ( application layer gateway ) that changes SIP and RTP messages passing thru the firewall to allow registration and open RTP ports needed on the fly.

 Most SOHO firewalls are not sip aware and you will have problems with Polycome phones - these phones are known to have problems with NAT , while providing very good ( I'd even say unmatched ) voice quality.

In addition your 3CX is behind NAT as well, making the whole communication picture a mess. Even with port forwarding enabled you most likely will see problems with phones not restringing or RTP not establishing.  

So the question is - What kind of fireawalls are you using ?

20120131-EE-VQP-002

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