SIP Trunk DNS names not resolving

[Ryan Foster]

Hi,

I'm fairly new to 3cx as a sys admin and I worked to upgrade the system from version 11 to 15 back in February, following the recommended upgrade path and not going from 11 to 15 directly.

All of the trunks worked perfectly well up until 3 weeks ago. I was forced to change the trunks from FQDN to direct IPs which is not ideal.

The server has been set to use Google IPs all along, and I am able to NSLOOKUP all 3 trunks and can PING all 3 trunks using their FQDNs.

But when checking the dashboard while test calling, I consistently run into this error:

Call or Registration to 1800xxxxxxx@([email protected]) has failed. 0.0.0.0 replied: 503 No DNS results; warning: No other DNS entries to try (0,0); internal

This happens for my NexVortex and FreeConferenceCallHD trunks as well. They only work if I switch them to a direct IP.

Just not sure what could have suddenly cause this "break".

Thanks in advance for any help or suggestions.

 

[leejor]

warning: No other DNS entries to try

This warning would seem to indicate that there are no DNS servers datafilled, or the DNS servers that are there, have a problem. If you open a Command Prompt window, in Windows, and do a tracert on the FQDN, what are the results? Do you get the correct IP?

 

[Ryan Foster]

Here's what I come up with for one of the trunks, freeconferencecall (attached):

 

[Ryan Foster]

In the meantime, I'm going to grab an old Windows 10 pc and slap a free copy of 3cx and get that configured in a test env. to see if the problem is with the operating system or network related. It's just so weird that it all stopped out of "nowhere", -_-.

 

[leejor]

And does that indicate that DNS resolves to the correct IP? If it does, then the machine running 3CX may not be able to do a proper DNS resolution...incorrect DNS server, or other network issue.
Have you tried using Googles DNS server... 8.8.8.8 , as a test?

 

[jed]

Just a shot in the fog but you could try to flush your DNS ipconfig /flushdns
Do you use 8.8.8.8 as primary DNS, or 8.8.4.4?

 

[cobaltit]

So in v15.5 3CX can make a decision based on SRV records as far as how it will connect to your provider. See this thread:

https://www.3cx.com/community/threa...but-3cx-cant-resolve-fqdns.55968/#post-232898

 

[YiannisH_3CX]

So in v15.5 3CX can make a decision based on SRV records as far as how it will connect to your provider. See this thread:

That does not seem to be the case here (at least for the mentioned registrar) as there are no SRV records for "voice.freeconferencecallhd.com" just an A record so the PBX should not have any issues resolving the IP.