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I have a Windows server 2008 r2 DHCP server that seems to be creating duplicate DHCP Leases.

For example If i have a workstation named Workstation1

It will create two dhcp leases with two different ips for the same workstation. workstation1 workstation1

Any ideas whats causing this? I do have DHCP conflict detection on, but my understanding it only applies to IP's has nothing to do with hostnames.

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two connected ethernet cards? – mdpc Dec 3 '12 at 19:42
up vote 2 down vote accepted

Having two network interfaces that aren't teamed together, and are both set to get an address over DHCP will cause this.

Your workstation has two NICs, doesn't it? And they're not teamed, right? Both set to get an address over DHCP too, I bet.

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I believe your correct. How can I resolve this problem? I assume Its problem with Laptop using both NICS, Ethernet and wireless. – Sarge Dec 3 '12 at 19:31
@Sarge That is completely intended behaviour. You will have to disable or disconnect one of them. FYI: The OS will normally use the interface with the best throughput (usually wired) for it's traffic and the other one just as a standby in case the other interface looses connection. There is no way to avoid getting 2 ip-addresses unless you team the interfaces (which not all OS or drivers can do) or simply don't use one of them. – Tonny Dec 3 '12 at 19:42
@Sarge what's the problem here? You could disable one of the NICs when the other is active (there's even a GPO for that), but if it's not causing you issues, I'd leave it alone. My workstation has 2 IPs, and it doesn't bother me... – HopelessN00b Dec 3 '12 at 19:43
I guess what I am wondering about is duplicate DNS entries but with different ips. – Sarge Dec 3 '12 at 19:46
@sarge Depends on your client settings, generally one IP will overwrite the other one, though. So, essentially, they'll both register as being the IP for your hostname, but the one that registers first will get overwritten by the one that registers last. – HopelessN00b Dec 3 '12 at 21:24

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