Solved Deskphones don't register upon failover from production system

[dashbrook]

Our internal deskphones are not registering with the failover server after the failover process happens. The phones are set to register with the public DNS name of the 3CX system. The public DNS name has been put into our internal DNS structure and it resolves to the correct internal IP address. During the failover process, the public version of the internal IP address of the active system is changed to the IP address of the failover server.

The failover server comes up normally and becomes the active server. Everything seems to be fine except for the deskphones. I rebooted one deskphone as a test and the result was the same. It would not register with the failover server.

Once I switched back to the production server from the failover copy and switched the IP address in the DNS system, the deskphones registered again automatically.

Ideas?

 

[JohnS_3CX]

Hi @dashbrook

How long would you say you left the phones after the failover event and DNS entry was updated?

 

[dashbrook]

5 minutes. The internal IP address was updated on one of many primary DNS servers within our network. Do you think I should try updating the internal address on all of our DNS servers thinking it is a DNS replication issue?

 

[JohnS_3CX]

Yes, it might be a matter of DNS. The phones will also take some time to notice that the DNS entires have changed based on the TTL, assuming the DNS server query response they got contained the new IP.

The 5 mins may have not been enough in this case, or perhaps they were getting a query response that still contined the old IP.

I think its worth looking a bit further into it, especially if you can monitor their DNS requests to see what reply they got back during the event

 

[dashbrook]

It appears the issue was with the multiple DNS servers. After adjusting the IP addresses on all of them manually instead of waiting for DNS replication to occur, the phones registered as expected. I don't know exactly how long it took for them to register since I had other business to attend to during the failover process but they did register. The TTL may have been a factor but I did not adjust that portion of DNS.

 

[JohnS_3CX]

glad to hear it was resolved!