[cisco-voip] Looking for insight into how Cisco 8851 deals with DNS TTL

[Russell Goings]

Hi all
   I have a client who was doing some network mucking around and part of
that maintenance caused the two DNS servers used by a group of IP phones to
go unavailable.  Some of these phones went unregistered with a reason code
13 - TCP KeepAlive Timeout.

What I (OK not me.  Just the client.  Well maybe I am interested as well)
would like to know is how do the Cisco SIP phones, particularly the 8851
model, deal with the TTL from the DNS response.

Does the phone honor the DNS TTL and cache the response for 24 hours?

Does the phone have a different cache time for the DNS response?

Does it make a new DNS query every time it sends a keep-alive?

I have never looked into this before and on this Thursday afternoon my
Google-fu is weak.

And the incident was over a week ago so not much from the phone logs to
help.

Thanks

Russell Goings (AM)
IPT Engineer – Dimension Data
Direct Line 571-203-4021
russell.goings at dimensiondata.com
Monday – Friday 8:00 – 5:00 EST
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