Question : DHCP Leases for Laptops...

Hello everyone,

At my organization, we have currently had an influx of laptops (300+) between two campuses.  Half of them plug in due to docking stations, and others are strictly wireless.  The ones that are plugged in, keep their wireless cards turned on (mainly just not knowing how to turn it on or off, and as small as the department is, we don't have the time to properly train each and every individual on how that works).  DHCP is starting to get kind of full at both campuses, due to a lot of laptops getting 2 IPs, and somehow seems to stack up different IPs for the same MAC addresses - I guess because they take them home, bring them back, etc.

What I am wondering here is:  Is there anyway for DHCP to determine if the device is, in fact, a laptop (or deeper, iPhone/smartphone), and if so, give it a lease only while it is signed on?  I would like for DHCP to hand them a lease, then upon them dropping the connection, the address go back into the pool.  We use Windows Server 2003 for our DHCP servers, and HP MSM310 WAPs for the wireless, if that matters.  At the current time, we're just using a WEP key as a (very) temporary security measure until we get the access controller up and running.

Any advice on how to accomplish this, or if it is even possible would be great!  Thanks.

Answer : DHCP Leases for Laptops...

Are your two DHCP servers sharing a range; i.e. DHCP1 serves 1 to 127 and DHCP2 serves 128 to 254?

You said your lease time is high, how high? I've never seen a reason to increase it beyond 3 days. I've only reduced it when addresses are short. DHCP isn't a high traffic process.

There is no way to change the lease based on AD or machine type. It's a pretty dumb process but I'm concerned that DHCP isn't really your problem. How many subnets have you got? What are the lengths of the masks in use? Give me different IPs if you're concerned about confidentiality. High DHCP leases on the desktops will cause problems, i.e. if you've changed it to weeks or months. As I said, I've never seen a reason to increase it beyond 3 days and that's on sites with thousands of desktops.