[ntp:questions] Source address in response always the same as target address in request?

Danny Mayer mayer at ntp.isc.org
Mon Dec 24 14:56:12 UTC 2007


Richard B. Gilbert wrote:
> I believe that there is a solution to the DNS caching problem.  Each DNS 
> record can be given a "Time To Live" or TTL.  If you are planning to 
> change the record, set the TTL to seven days, then six, five, four, 
> three, two, one. . . .  All of those cached records should expire at 
> more or less the same time.  It's not perfect but it works.  If you time 
> it just right, you can minimize the amount of disruption.
>

This is exactly how we tell people who are changing IP addresses of the
DNS servers for a zone to migrate. We also tell them to keep the old
server running for a short while after the changeover but handing out
the new NS records of the new server(s). After requests stop coming in
to the old server then it can be shutdown permanently.

Danny



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