Min/Max Refresh and Notify

Kevin Darcy kcd at daimlerchrysler.com
Fri Dec 13 17:18:05 UTC 2002

Mike Diggins wrote:

>I have a slave name server configured with a zone using min and max
>refresh time. 
What do you mean by "min and max refresh time"? There is only one 
REFRESH field in an SOA record.

>I was using it to limit the number of times the zone updates
>to just two times a day.
>Question: If the master name server is configured to send notifies to the
>slave when an update to the zone occurs, will the slave update the zone
>anyway? That appears to be what's happening but I want to be sure. If it
>is true, would turning off notifies to that slave for that one zone stop
>that from happening?
Yes, you could turn off NOTIFYs and that would greatly reduce the number 
of refresh checks that the slave performs. But, be aware that the 
frequency with which BIND slaves perform refresh checks has a random 
element to it. This is done deliberately to prevent slave "cycling" 
which causes spikes of refresh-check and/or zone-transfer activity. So 
you can never *exactly* control when the slave will perform 
refresh-checks when you rely on the REFRESH setting alone.

Perhaps you might consider turning off NOTIFYs to the slave within BIND 
and then using an artificial non-BIND method of sending NOTIFYs to the 
slave at specific intervals. I seem to recall there was a utility out 
there that could generate NOTIFYs, but I don't have a pointer to it 
handy. Perhaps someone else on the list could provide that information...
                                    - Kevin


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