Hi guys,

I have been using Elastix with Linksys phones without a problem however the company upgraded all phones to Yealink SIP-t28P's. Great phones, very clear however problem is, there is only 1 way audio. The called party cannot hear ANY voice.

I have enabled RPORT, UDP keep alive etc. Everything registers and I can make outbound calls and hear the other person, just cant receive voice.

Has anyone got any ideas what could be causing this? One other problem is that some times, maybe once after a reboot, it works perfect, then stops.

I am running a wireless network adapter to the phone as I dont have ports in every office. This though, hasnt been a problem with the Linksys phones.

Does this issue happens with all Yealink phones?
What about if you connect another phone where the yealink is supposed to be, do you have the same issue?

We use quite a few of the T26,T28, and T38G's. No issues here. Are they on the same LAN as the pbx?

Hi, yes all Yealink phones. Linksys phones work fine so I dont understand why another IP phone wouldnt work too.

I am not on the same LAN as the PBX. It is in a datacentre off site however, I have made sure all ports are forwarded correctly. We have 3 remote offices. 1 has Linksys phones, 1 has Bria3 softphones and my office has the Yealink phones. All work perfectly, except mine.

The set up is:
ADSL2+ business link on static IP
Wireless ADSL router in the data room
Netgear wireless adapters to make the phones LAN wireless
No firewall at the office
PBX in offsite datacentre with firewall and all ports forwarded

Like I mentioned in the original post, sometimes (once or twice) the have worked. I was able to call my mobile and leave a message but when I tried to call again, no voice was sent.

If they are registering, I would bet anything it is a NAT issue. Make sure to turn off any SIP ALG if they are enabled on your router or firewall. I know the Yealink phones have an issue with Dlink and the SIP ALG turned on.

Hi,

I found the SIP ALG in the wireless router and disabled this however still nothing. I have a datacentre checking their firewall settings but does anything else come to mind?

Make sure to reboot the phones and router after disabling the SIP ALG. What firewall are you behind at your data center? It is NAT'd correct? Is sip_nat.conf configured correctly?

Yes its all Nat'd correctly as the Linksys phones work in 4 other locations.

I disabled SIP ALG at the datacentre level and all phones started having the same problem, even the ones that were working previously.

I not 99% sure I rebooted everything after making the changes but will check again once back in the office.

Thanks for your suggestions.

Hi,

So I have rebooted everything, disabled SIP ALG on the firewall but this breaks connection to all Linksys phones.

Any other ideas?