Remote SIP Phones occasionally drop out and dont register


I have several remote extensions on different sites. From time to time an extension will drop out and not register with the PBX. Sometimes it will come back on and sometimes the problem will arise on a differnt extension. Anyone experienced this? Is it something to do with ports?

I have searched for an answer but so far found nothing.


I never do understand why people go changing the port values on the phone. Do you ever have trouble with multiple web browser sessions open at once? They all work through port 80.

The SPA’s have keep alive settings that should be able to be set aggressively enough for even the most aggressive firewall.

You could also run a VPN back to the main server and save yourself all of these headaches.

We have the PBX at one location and remote SIP phones connect to it. The PBX has a Static IP so we connect using that.

If it would help to supply any additional info please let me know. Thanks for your replies.

“Not register with the PBX” meaning they don’t try and re-register, or just that the phone goes UNREACHABLE until it re-registers? If it’s the former, probably connectivity problems. If it’s the latter, it could be your firewall closing holes too soon. Try setting [font=Courier]qualifyfreq=15[/font] on the extension instead of the default 60. This will mean the firewall hole only has to stay open for 15 seconds instead of 60.

Yes, it goes unreachable and then sometimes it may re-register all by itself, sometimes after rebooting the phone and sometimes it stays unregistered for ages and becomes very stubborn!

I use Linksys SPA942 phones. The have four channels. The phone I am looking at at the moment has an orange light. It’s the fourth light as I’m using channel for. I see on the phone config, the four channels are set to SIP ports 5060,5061,5062 and 5063 respectively. Does this mean than I change set the port in FreePBX to 5063 or keep it at 5060?

I have changed the qualifyfreq to 15 as suggested as it cant so any harm.

I am thinking it might be a port/firewall issue. Sometimes when I make calls, there is no audio. It gives the impression that a hole in the firewall has timed out.

Thanks for your response.

Changing qualifyfreq doesnt appear to have helped. The phone that was not registering came back a little later but another has gone off now.

Maybe NAT related. You haven’t specified what you are doing on both ends of this equation so it’s only speculation at this point. Also what your FreePBX NAT settings are.

Hi mustardman
Thanks for the reply. Specifically, what info should I post?

What is the configuration on both ends? Is the server behind nat and the phones behind a different nat? Important info if that is the case.

Likely NAT related but if you are using DNS try change to IP instead and see if that helps. Then at least you know the why.