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DNS Scavenging Questions

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Last Modified: 2012-08-13
We have a Windows Server 2003 / SP2 domain with AD-Integrated DNS zones.  We are accumulating a number of stale resource records from clients, and are having name resolution issues as a result.  I would like to enable DNS scavenging, but need to make sure I understand exactly how to do this.  I've read a number of articles on this, and based on that, I believe that just turning it on using the default settings (7 days) will work...our DHCP leases are all 8 days.  However, I'm not clear on a couple things.  1)  We have 5 AD-Integrated Primary Zones...only one of which has an issue with duplicate stale records.  Should I enable scavenging just for the one zone, or go with the option to "scavenge all zones"?  And how do I do this?  I've read some articles that say to just enable the options at the zone level...others state that you must select the "Set aging and scavenging for all zones" option on each DNS server along with enabling it at the zone level.  2)  If I must enable scavenging at the DNS server level, do I set the same options on both of our DNS servers, or just configure 1 to do the scavenging?  3)  Do I need to run the AGEALLRECORDS command before turning this on, or will it be OK since they were all already AD-Integrated zones?  Thanks.
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Thank you for the quick responses...just a couple follow-up questions.  If I follow the steps to "Set Aging and Scavenging properties for the DNS Server", and select the "Set Aging/Scavenging for all Zones" option at this level, is that all I need to do?  Or do I then need to follow the steps to "Set Aging and Scavenging" properties for a zone" in addition to this?  I just need some clarification on the locations of the different options I need to configure...the documentation refers to several different locations and don't clearly explain what scenarios require what settings.  Also, do I need to run the AGEALLRECORDS command on one or both DNS servers prior to enabling this...or should I be OK becasue the zones are all already AD-Integrated?  Thanks.

Commented:
NO DO NOT run ageallrecords.    From my understanding of this utility what it actual does is change the timestamp to the current time.  In other words it will actually make your current stale records valid.  (Denis  can you confirm on this?)

You need to configure it for all zones on the DNS server, and then configure each zone seperately.


Chris DentPowerShell Developer
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hi...

this is an exact quote from DNS on Windows Server 2003 by Matt Larson....

"A global setting controld aging and scavenging for the entire DNS server. It's located on the advanced tab of the ser properties window. The scavenging period setting controls how often the server makes a scavenging pass through all authrritaive zones.

Once aging and scaveging has been enabled on a given server, you must still enable it for a particular xone. From the general tab of a zones properties windows, click the aging button. "

Hope this helps - and make sure you leave the default options - just tick the boxes, nothing else....
Chris DentPowerShell Developer
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Commented:

Just to clarify slightly.

Dean is correct about how AgeAllRecords works. It copies the current timestamp into the associated field for each and every record within the specified zone. That includes any Statically configured records which can be undesirable.

Even with that set the records will not be scavenged until they have aged (again, based on the two aging periods expiring for the record).

Static Records do not normally carry a Timestamp and are, as such, never elligible for scavenging (unless a timestamp is forced as above).

As a side-note, AD's Service Records are automatically Refreshed / Updated once every 24 hours, so unless Aging is set exceptionally low will never be scavenged for a live DC.

Chris

Commented:
Thanks for the clarification Chris.

And to clarify a little more, the actual "configure server, all zones & then configure the zones themselves"  debate  really comes down to the OS, the DNS zone configuration, and the version.

My advice, and that's all we can offer here, would be to configure the DNS server, then check the zones, if they are configured then job done, if they are not, then not a big job to do it.  

Waiting for the we have 150 zones configured in our environment reply now :-)

HTH lakeviewmedical

Author

Commented:
So just to summarize the steps to take for this:
-  Go through each zone and verify that any static entries do not have the "Delete this record when it becomes stale" box checked.
-  Enable scavenging for all zones at the DNS server level (on both of our DNS servers)...leaving the default settings.
-  At the zone level, set aging parameters...again leaving the defaults.
-  Manually run a scavenging task using the "Scavenge Stale Resource Records" option at the server level.
-  Also at the server level, set automatic scavenging within "Properties / Advanced"...again leaving the default settings.
Is that all there is to it?  And also, we only have 2 Forward Lookup Zones for our facility...along with 3 other zones that are there as a result of zone transfers with a partner organization.  Do I enable scavenging on these zones as well, or just our own?  And after all the changes are implemented, is it required to stop / start the DNS service on each DNS server for the changes to take effect?

Thanks again for all the responses.
you got it....yes that is all that is required...

i am guessing the other DNS zones you have are secondaries, which in that case you can't write to that zone anyway...but even if its not secondary, best let the owners of the zone to do the scaveaging - im guessing you wou;ldnt have access to it anyway...

Author

Commented:
OK...and do I need to stop/start DNS for the changes to take effect...or will it be in place once I enable it?
it should take effect straight away....well as soon as the interval kicks in, but starting and stopping it won't hurt.....

Author

Commented:
-  I just thought of one additional question...if I set up both of our DNS servers to do scavenging, and they are both configured to run on the same schedule, won't this cause a conflict?  Is it OK to turn this on on both DNS servers, and go with the same default settings for automatically performing scavenging operations?
yes, that will be fine...they will deal with the changes accordingcally, and if they both make the same change at exactly the same time, the dc with the highest GUID will win and make the actual change...AD replication is a wonderful thing...
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