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3CX Flowroute DNS Failure

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Frank86

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Using 3CX with Flowroute at two locations. One is very stable. The other one has Flowroute go down multiple times a day, with the error message below. The only way to bring it up for a few hours is to change the SIP registrar in Flowroute and 3CX SIP Trunk.

Registration at Flowroute has failed.
Destination (sip:[email protected]:5060) is not reachable, DNS error resolving FQDN, or service is not available.


Is this a problem on my end? What could be the cause?
 
Are there other trunk groups that also seem to be affected? Are there remote extensions, that go down (Internet connectivity issue) ?

Have you spoken to Flowroute? Have you talked to the ISP? Do both locations use the same ISP?

Is it possible it is a modem, router, or other network hardware issue? Have you swapped out anything?

What DNS server do you use, have you tried using 8.8.8.8 ? Just to eliminate that.
 
Here's the thing; it only affects one of the two locations. I have opened a ticket with Flowroute, but no answer from them yet.

It could definitely be an issue on my end. For DNS, I'm using OpenDNS 208.67.220.123 and 208.67.222.123 at both locations.

The location that does not have problems has a dedicated 1:1 NAT rule in the firewall with a dedicated public IP for 3CX, using fiber.

The location that does have problems is not using a 1:1 NAT rule with dedicated static IP; it's using port forwarding rules on a static public IP address (on business cable) shared with other services.
 
So as @leejor mentioned I would start by changing the DNS on the box itself to Google DNS to see if that changes the behaviour.
 
I will change our DNS server's forwarders to Google later today and test.
 
So, I switched DNS to 1.1.1.1 and 8.8.8.8 and, after about 12 hours, it just went down again.
Flowroute support unhelpful so far.
 
Hello @Frank86

As you can see the error you are getting can be many things. Since the DNS is resolving correctly then you should focus on other things. Use the Activity log and see if any errors are generated at the time this happens. You could also run a a capture and try an outbound call. The issue might me something else. Also you didn't mention what happens when you get the error. Does the trunk un-register or do calls fail?
 
I will follow your advice and check other things.
Yes, when I get the error, the Flowroute SIP trunk unregisters, and all calls fail.

The only way to bring it back up right away is to log onto Flowroute, change the point of presence (registrar), then enter the info in 3CX > SIP Trunk > Flowroute and save.
 
Run a wireshark capture on the PBX machine when the issue begins and check for registration messages to the provider. This will tell you if the registrar is sent to the correct IP and is the provider responds with an error or not.
 
I was having this exact same issue with a Windows install of 3CX and tried using several different DNS servers. My latest attempt at fixing it was to disable IPV6 and so far it's been working fine for probably a month or more now. I'm hoping that was the fix.
 
I spoke too soon. Literally I just now got a call that their phone calls started getting the DNS error again. If I reset the SIP server it starts working again. I checked settings against another Flowroute and 3CX setup and made some changes that I saw were different (mostly that Put Public IP in SIP VIA header wasn't set).
 
Run a wireshark capture on the PBX machine when the issue begins and check for registration messages to the provider. This will tell you if the registrar is sent to the correct IP and is the provider responds with an error or not.
Will do. thank you.
 
I was having this exact same issue with a Windows install of 3CX and tried using several different DNS servers. My latest attempt at fixing it was to disable IPV6 and so far it's been working fine for probably a month or more now. I'm hoping that was the fix.
Mine is a Linux 3CX install that I inherited and was on an AT&T PRI.
 
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