Destination (sip:X.X.X:5060;lr) is not reachable, DNS error resolving FQDN, or service is not available.

[Roopesh Balakrishna]

Dear Support,

We are frequently experiencing SIP registration issues. We are using an Etisalat SIP connection that is connected to our core switch. The SIP connection goes down intermittently and comes back only after restarting the core switch.

This issue is severely impacting our daily operations and business communications and requires urgent attention.

 

[TheodorosG_3CX]

This is a networking issue. Since you mention that after a reboot of the switch this is resolved, then you need to check on that side.
The error shows that DNS resolve is not coming to the NIC of the PBX server.

 

[YiannisH_3CX]

Hello Roopesh,

Are you using a direct SIP trunk over the internet or a gateway to connect your PBX to Etisalat? How does your set up look like?
If you are using a gateway what type is it and how does it connect out? Do you have an analog line coming to it?