DHCP & PXE boot workstations

[DOYLE FOSTER]

We are trying to implement PXE boot for workstations to enable re-imaging of the workstation, and have run into an issue with DHCP handing multiple IP addresses to the same workstation.  I have reviewed previous list entries regarding multiple IP addresses for the same mac address.  One response suggests identifying the UID in the leases file, and reclassifying the 'temporary' address into a pool with shorter lease times.  I tried this with one workstation, and the results are different that expected.  

I started with a new workstation that had never been on the network before.  They ran it through the entire PXE boot and imaging process.  Checking the leases file I found 5 IP addresses for this mac address with no UID listed, and 2 IP addresses with exactly the same UID listed.  I thought I understood that a subsequent request from the same UID would be given the same IP adsress.  Not sure what to expect for a request with no UID.

My overall problem is the exhaustion of my DHCP pool with multiple addresses.  I am running ISC DHCP Server V3.0.4

Why would I see 2 IP addresses with the same UID and mac address?
Would it be possible to classify the request differently based on the lack of a UID?  
Anyone with experience dealing with the PXE boot process?  

Any suggestions appreciated.

Thank you,



Doyle Foster
Data Communications Engineer
Sallie Mae
Network Services
317-595-7173
dfoster at salliemae.com