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DHCP Lease Durations

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by steve w brookes

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This may sound like a silly question but why is it recommended that DHCP lease durations are reduced in a Windows Server 2003 environment when mobile devices are used.

I can understand roaming allocations where the lease would be very short but why bother in an office environment even if the mobile units are often disconnected and reconnected from the network.

I have come across several sources now that recommend shorter durations than the default 8 days when mobile devices are used including a publication from Microsoft itself but can find no logical reason why this should be.

Hope someone can help.

3 replies

by flycaster

Hi Steve,

The lease time you should chose is dependent a few factors :

- How many ip addresses do you have in a dhcp pool
- How many devices connect and need an ip address.
- How frequent do devices connect and request an ip address.

If you have a lot of device connecting with limited ip addresses you need a shorter lease time. IP addresses get freed quicker and device do not get a denial on a dhcp request.

If the lease time is to long, ip addresses are not given back to the pool quick enough although the ip address might not be neccessary any more because the device has already disconnected. The ip address(es) cannot be used as a result of this and other cannot get an ip address if all addresses are given out aka "in use".

Hope this helps.

by steve w brookes

Thanks for that, I guess the key point there for me is the address pool which I hadn't really considered but does make sense.

Notice you are from Norway, I hear it is a beautiful place and is on my short list of places to visit and spend some time. I hear the fishing is pretty good there too - all the more reason to visit :-)

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