FQDN doesn't resolve in cellular network

[cjferoussis]

Hello, I have a problem and I hope someone here will help!
We have been using 3CX for more than 10 years. Everything works fine: the app connects both in office and out of office regardless if we use WIFI or LTE.
The problem arose when we decided to use the live chat on our website.

It seems that the FQDN does not resolve if connected via LTE.
Any phone can connect to the server if connected via ANY WiFi but not via LTE.
Interestingly, if the phone connects to a WiFi hotspot from another phone, the server responds as expected.
If we use the (dynamic) IP ( https://<external.ip>:5001 ) we can connect even if we use LTE.
Nslookup resolves correctly and from inside the LAN, DNS resolves it directly to the internal IP of the server.

With all this trouble, Live chat appears in our website when on PC or WiFi but not when on LTE.

Could someone help?

3CX Version; Standard Annual18.0 (Build 23) On-premises
Server OS Win 10 (I know, I work with what I have)

 

[Evolute IT]

Run a firewall checker to see if any ports are getting blocked from the server side.

Then, run a DNS Checker for the FQDN and check that all nameservers respond with the right IP (probably dynamic so confirm that it's the good one.)

If your IP changes a lot, you'd be better off in the cloud. Standard/Pro have a 6h DNS TTL so it can take a while for the IP to update everywhere, and many carriers have DNS caches that have stupidly long TTL.

 

[cjferoussis]

Thank you for your reply!

DNS Checker resolves correctly.
Our IP does not change a lot (max once every 2-3 months), so we have no problems regarding that.

Firewall checker is another problem we face and currently trying to solve:

• resolving 'stun-eu.3cx.com'... done
• resolving 'stun2.3cx.com'... done
• resolving 'stun3.3cx.com'... done
• resolving 'sip-alg-detector.3cx.com'... done
• testing 3CX PhoneSystem 01 SIP Server... failed (How to resolve?)
  • stopping service... done
  • detecting SIP ALG... not detected
  • testing port 5060... full cone test failed (How to resolve?)
  • starting service... done
• testing 3CX PhoneSystem Media Server... failed (How to resolve?)
  • stopping service... done
  • testing port 5090... done
  • testing ports [9000..9398]... done
    • [...]
    • testing port 9398... done
  • testing ports [10600..10998]... failed (How to resolve?)
    • testing port 10600... full cone test failed (How to resolve?)
    • [...]
    • testing port 10998... full cone test failed (How to resolve?)
  • starting service... done

all ports are forwarded correctly, and there should be no firewall conflict.

 

[cjferoussis]

Hello, I have a problem and I hope someone here will help!
We have been using 3CX for more than 10 years. Everything works fine: the app connects both in office and out of office regardless if we use WIFI or LTE.
The problem arose when we decided to use the live chat on our website.

It seems that the FQDN does not resolve if connected via LTE.
Any phone can connect to the server if connected via ANY WiFi but not via LTE.
Interestingly, if the phone connects to a WiFi hotspot from another phone, the server responds as expected.
If we use the (dynamic) IP ( https://<external.ip>:5001 ) we can connect even if we use LTE.
Nslookup resolves correctly and from inside the LAN, DNS resolves it directly to the internal IP of the server.

With all this trouble, Live chat appears in our website when on PC or WiFi but not when on LTE.

Could someone help?

3CX Version; Standard Annual18.0 (Build 23) On-premises
Server OS Win 10 (I know, I work with what I have)

-mistaken post-

 

[cjferoussis]

- mistaken post-

 

[SweetAction]

Custom FQDN or 3CX FQDN?

 

[cjferoussis]

It is an 3cx FQDN!
xyz.3cx.gr

 

[cjferoussis]

We have solved it. The problem is related to the IPv6. For some reason, there is no response when DNS resolves to IPv6. We disabled it on the server side and everything works fine!