PXE client receiving two IP addresses.

Simon Hobson dhcp1 at thehobsons.co.uk
Mon Jan 24 07:56:17 UTC 2011

Pooja Gada wrote:

>We have been facing a problem with respect to the PXE clients, the 
>DHCP Server is assigning two different IP addresses to the same 
>device,  one for PXE client and other when the machine boots up.
>Has anyone faced a similar problem ?
>And, is there is a workaround ?

Yes this is a known problem. The RFCs require that the Client-ID is 
used as the primary key if present, and fallback to using the MAC 
address if the client doesn't supply a Client-ID. Since MS chose to 
supply a Client-ID by default (which is allowed) which nothing else 
does, then the server treats them as two different clients.

There were some patches to deal with this by (IIRC) setting the 
Client-ID to the MAC address if it wasn't supplied - thus making 
other clients behave like the MS ones. I don't know if they are still 

Or, write a class that matches PXE clients, and give them very short 
leases from a different pool.

You should find something if you search the list archives - it's 
popped up regularly (and been answered) quite a few times over the 

Simon Hobson

Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed
author Gladys Hobson. Novels - poetry - short stories - ideal as
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