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Having second thoughts about DNS Scavenging...should I or should I not?

Posted on 2009-05-07
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Hi, I am having second thoughts about DNS scavenging...should I or should I not?  I have been having issues with one of my zones off and on for about 6 months with A records sharing the same IP addresses and have manually deleted the old records by checking the DHCP server to verify the correct IP for the specific machines.

I have enabled DNS scavenging a couple weeks ago, but now am concerned that it may delete legit records.

So, do you use DNS scavenging?  If not, how do you manage your DNS?

Just a bit concerned noob,

Bob
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Question by:rsnellman
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Author Comment

by:rsnellman
ID: 24325969
Oh, forgot to mention, that one of my biggest concerns with scavenging, is I have records that were created manually and I am a bit afraid scavenging may delete them.

I have scavenging set:
No-refresh interval : 4 days
Refresh interval: 5 days


Any reassurance would be greatly appreciated.
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by:KCTS
KCTS earned 50 total points
ID: 24325978
Scavenging will only delete records that fail to re-register themselves - so their should be no issues with legit record being deleted.
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Author Comment

by:rsnellman
ID: 24326048
Ok, I may have just found my own answer...but I need a second opinion.

It looks like NS (Name Server) records are not included in the scavenging, also each A record has the "Delete this record when it becomes stale" and the "Record time stamp" date.  So, if this box is checked then it is included in the auto scavenging process.  Right?

So, if there are records in my zones that I do not want to be included in the auto scavenging process, I just make sure this box is unchecked?

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Author Comment

by:rsnellman
ID: 24326102
One more question...I have noticed that under the Name Servers tab of a NS record, I am showing a couple of servers that are no longer running DNS Servers, but I have just enabled auto scavenging a couple of weeks ago, so is it possible that scavenging will remove these for me or do I have to delete these NS records manually?

Sorry if I may be asking the same question, but I am just wanting to make sure I understand this process.
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Author Comment

by:rsnellman
ID: 24326191
So, does this auto scavening only apply to dynamic DNS entries?  I have noticed that it seems that the dynamic DNS entries have the "Delete this record when it becomes stale" checked and the manual DNS entries (that I am sure where created manually) do not have that option checked.  Is this correct or am on in left field again?

Thanks.
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Author Comment

by:rsnellman
ID: 24326315
I know, I am being a pest, sorry...I was wondering what happens when say, I have a backup machine that I do not have on all the time and the auto scavenging tries to verify this machine still exists and then decides it doesn't and deletes the record?  The next time I turn on the backup machine, it will just re-register and grab or create a new record and go on about its business?

Thanks again.
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Accepted Solution

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Chris Dent earned 450 total points
ID: 24327169

> Oh, forgot to mention, that one of my biggest concerns with scavenging,
> is I have records that were created manually and I am a bit afraid scavenging
> may delete them.

Scavenging will not effect manually created records. Only dynamically created records.

> So, if this box is checked then it is included in the auto scavenging process.  Right?

Yes (and yes to the follow-on question).

> Stale NS Records

Depends a lot on how they were added. It's perfectly safe to delete them though if they're lingering. Shouldn't be many changes for those so they don't tend to fall into Scavenging discussions.

> So, does this auto scavening only apply to dynamic DNS entries?  

Unless you manually set a record to be scavenged (the tick box you found), yes.

> it will just re-register and grab or create a new record and go on about its business?

Yes. Regardless of how the machine gets its IP address the DHCP Client service is responsible for registering Host (A) records and Pointer (PTR) records. It will do that when you run "ipconfig /registerdns", or when you restart the DHCP Client service.

As it does that when the service starts it will also register when the server starts :)

To make life a bit odd...

The DHCP Client Service only registers records for systems receiving addresses from DHCP if the DHCP Server is *not* updating on the clients behalf. The DHCP Client service updates DNS for clients with static IPs regardless.

HTH

Chris
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Author Comment

by:rsnellman
ID: 24327405
Thanks for the reassurance.  You all are the best.

Have a wonderful day.

Bob
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