DHCP Lease duration not cleaning expired leases and messing up DNS.

I have computers that have been unplugged from my network and taken out of the LAN. Their leases still exist and were eventually assinged to an active computer. This is causing multiple IP addresses to one active computer and a couple inactive computers. I am trying to get the lease duration to remove this left over data. It's not working and I don't know what I am doing wrong.

Since I have DHCP Dynamically updating DNS records, and DNS scavaging through the zones, my DNS records are also showing multiple computers on the same IP as well.

Now, you would thing this would totally hose up the network. It doesn't seem to effect it at all. But, I just like running a tight ship and hate to see left over data from something that doesn't exist.

FYI: This is the way DHCP is set up. I set it up this way, in case one server goes down the other will administer DHCP.

Fixed IP:
10.49.10.1-10.49.10.50

Server 1:
Scope: 10.49.10.51-10.49.10.152
Lease Pool: 10.49.10.51-10.49.10.151

Server 2:
Scope: 10.49.10.152-10.49.10.252
Lease Pool: 10.49.10.152-10.49.10.252

DNS scavaging set to default of 7 days
DHCP lease duration set to default 8 days.

note: No overlapping scopes or rogue DHCP servers, I have checked may times for Rogue servers.
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ChiefITAsked:
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Brian PiercePhotographerCommented:
If as you say the scavenging is set to the deault then there is a 7 day "no refresh" period followed by a 7 day "refresh period" which means record will not actually be scavenged until the 15th day. I think this is the root of the problem.
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ChiefITAuthor Commented:
Hey KCTS:

Thanks for the quick reply!!

Do you think that will also cause the DHCP leases of computers, that are no longer on the network, to remain?

I forgot to mention one other fact that I was debating about. I don't delete computers, I disable them in AD. I was thinking these disabled computers are holding onto the lease and the lease duration will not remove these leases as a result.

Please advise.

BTW, this will not be an abondoned question and full credit will be given out. I wish I could make this a 1k question.
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ChiefITAuthor Commented:
KCTS:

I guess this was a two part question. I solved one part. You got the other for full credit.  

DNS Cleanup:  

I reset the scavaging ages as you recommended to 3 and 5. That will be a 9 day turn around and make it one day longer than DHCP.

DHCP cleanup: (resolved)
I said "da' heck with it" and deleted the AD computers SIDs. DCHP leases immediately cleaned right up. Not a single "old computer"  IP address remained. I didn't expect a disabled computer to hold onto a DHCP address, like it did. Now, I know.

On a Personal Note:
You know, I am glad you showed up, you're one of my favorites on EE.

Thanks!!!



 
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