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IP Phone DNS Cache

Hi there, sorry if this has been answered I was not able to find exactly what I was looking for.

 

We have a single CUCM cluster on version 12.5 with the servers defined by FQDN in system > server.

  • 7800 and 8800 phones.

 

I was curious if we have an outage with our central primary/backup DNS servers, how long will the IP phones cache the record for the CUCM server to continue to stay registered ?

  • If the specified TTL expires on the cached record for the phone will it unregister?

 

Thanks!

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Re: IP Phone DNS Cache

Anyone ? or any other details I can provide ?
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VIP Mentor

Re: IP Phone DNS Cache

The phone will use the TTL value to expire it's cache entry after which it will try to contact DNS again. If there is a DNS outage, from experience the phone will continue to use its old entry. Phones are a little stubborn and don't give up their configuration easily..

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