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We had a problem yesterday where one of our DHCP servers had a scope run out of IP addresses. We expanded the scope's range of IP addresses only to find out that it impinged on the 2nd DHCP server's scope, that still had IP addresses available for lease.

Let's say original was:

DHCP SERVER 1 = 10.10.8.50-150/24
DHCP SERVER 2 = 10.10.8.151-250/24

and the change was:

DHCP SERVER 1 = 10.10.8.50-200/24
DHCP SERVER 2 = 10.10.8.151-250/24 

Why the clients didn't get told "go to DHCP SERVER 2 and try there", I don't know, since both DHCP servers are set in the routers for bootprelay.

So, long story short, I ended up SHORTENING the scope of DHCP SERVER 2.

Final config:

DHCP SERVER 1 = 10.10.8.50-200/24
DHCP SERVER 2 = 10.10.8.201-250/24

The problem now is that some of the clients that had a lease before the problem are now refusing to get an IP.

The DHCP server logs show similar to:

> 11,07/22/11,08:23:32,Renew,10.10.8.170,DEVICE01.mydomain.local,XXXXXXXXXXX,
> 11,07/22/11,08:23:38,Renew,10.10.8.170,DEVICE01.mydomain.local,XXXXXXXXXXX,
> 11,07/22/11,08:23:43,Renew,10.10.8.170,DEVICE01.mydomain.local,XXXXXXXXXXX,
> 11,07/22/11,08:23:48,Renew,10.10.8.170,DEVICE01.mydomain.local,XXXXXXXXXXX,

The client is reaching the DHCP server, and keeps asking for the same IP, AND the DHCP console shows this client getting this IP address...but the client ends up with a 169 private address instead.

The client continues over and over to get an IP and the logs show the above...but still the client won't get an IP.

I've tried rebooting the DHCP servers, rebooting the client, doing IPCONFIG /release and /renew, disabling the NIC and re-enabling the NIC, moving the PC to another part of the building, still no luck.

Any help is appreciated, before I end up calling Microsoft.

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2 Answers 2

Have you tried clearing the server cache and data files? also if there is an existing lease on the same IP, have you tried removing that?

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existing lease deletion, yes. Clearing the cache and data files no. How do I clear the server cache and data files? Will doing so cause EVERYONE to get a new IP address? Right now there are only about 10 computers affected, so I'm very worried about causing hundreds to be affected. –  TheCleaner Jul 23 '11 at 16:52
    
clearing server cache is an option on the right-click menu when you right click on the server name in the Microsoft DHCP console. It wont cause machines to get a new IP address. –  Bahrain Admin Jul 25 '11 at 7:40
    
You sure you aren't thinking of DNS? I don't see such an option in DHCP. –  TheCleaner Jul 25 '11 at 12:56
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up vote 1 down vote accepted

The server cleared itself up on its own...sorry for just now closing this. The following Monday everything was fine again.

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