IP Phones hostname are flooding the DNS server

[m.alkhateeb90]

Greetings,

We recently upgraded a client IP Telephony infrastructure to CUCM ver 11.5, and added a new IP subnet to the IP phones. After the phones obtain their IP addresses from the DHCP server they automatically register them selves as a DNS entry with their hostname (e.g SEP001122334455).

I consulted a Microsoft Engineer and he advised this might be a feature in the DNS server where the endpoints can add their hostname as an A record, but for this to happen you have to enable the feature from the endpoints.

Any one encountered the same? Is their a feature maybe in the call manager 11.5 that does the same? Also note that this happens in one subnet only not all the subnets.

[R0g22]

SEP001122334455 >> this is not a DNS entry. There should not be a need for a A/SRV record for this. This is the device identity you might say. Does your CUCM cluster use FQDN or IP addresses ?
That would be a reason why would you see DNS requests from phones going out to your DNS.

[m.alkhateeb90]

Hi Nipun,

the attached screenshot is showing the problem.

[R0g22]

You did not respond to all my questions. Are you servers configured with FQDN ? Where do you see these logs ? And what is the issue ?

[m.alkhateeb90]

Dear Nipun,

The server is configured with IP not FQDN.

The attached screenshot shows the DNS A record entries not LOG file. They appear in the Microsoft DNS Server.

[R0g22]

Honestly, I am still not sure what the issue is. Why do you have A records for the phone device name in your DNS ?

[m.alkhateeb90]

That’s exactly my issue, why there is IP phones hostname A record in the DNS server without me adding them?

[R0g22]

Interesting, never seen that before. Are you sure no one else has access to the server and was not trying to play around some phone registration issue ? Delete those and then monitor.