Solved DHCP Lease not dropping computer name from DHCP

July 25, 2012 at 13:09:51
Specs: Windows Server 2003
When a computer is connected to our network then disconnected the computer name stays on my DHCP list and fills up my Lease IP's. Now I have 85 percent full, but not all are actively being used. How can I take the computers that are not on my network anymore off the DCHP List (Scope - Address Leases)?

Can I just right click and select delete? (will it be available again for another pc that joins the network) Or is there a better way to clean up my DHCP?

Thanks in advanced


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July 25, 2012 at 13:44:48
✔ Best Answer
DHCP leases last, by default, for 8 days on Windows 2008. After that time they will automatically be released. If that is causing you problems then you can alter the period for which leases are retained. But I wouldn't bother if it is not actually causing you problems. It is slightly more efficient to reuse an existing lease than to create a new one.

See for details of how to alter the lease retention period.

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July 25, 2012 at 13:51:41
Thank you for the reply. When the DHCP was setup (don't know who did it) but they set the expiration to infinite.... therefore all computers are retaining the IP address even though these computers are not on my network (not even in the same state

I am setting all the leases to 8 days, however, the ones that were originally on the DHCP are still infinite.

If I just right click and delete - that should free up the IP correct and make that IP available and free'd so it can be used again?

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July 25, 2012 at 14:35:22
If you are sure that the client is never going to contact the network again then you can just delete the lease. As you say, that will make the address available for reuse. But for leases that are in use still you should release the lease on the client, delete the lease on the server then renew the client lease. Otherwise you are going to get IP address conflicts.

As the link I gave says, and as you have discovered, indefinite leases are not a good idea!

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July 25, 2012 at 18:25:03
Thank you for the reply. We have some leases from corporate people that came to the office once, and also, sales people that come in every now and then. I figured if I right click and delete these lease, and if they ever come back to the office, then it will assign them a new IP. Also, there are PC's that have been taken offline that I don't think will ever be brought back up.

Its just scary to delete one and see it disappear from the address pool. I feel like I deleted it for good :)

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July 25, 2012 at 23:15:40
I'd recommend that when those computers next come into the office you do a "release/renew" lease on them. Otherwise you may have conflicts.

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