status update

SCOTT BURGIN sburgin at
Wed Dec 13 02:30:22 UTC 2006

With regards to PXE and dual leases per physical machine - we're still
figuring out which of the earlier suggestions best suits us long term.
In the short term, we have thrown more addresses at the problem -
creating a second subnet on the same VLAN (Cisco environment - using the
"secondary" keyword").
However, we're having an issue where the machines in the new/secondary
subnet can't complete their PXE process.  The vendor is telling us that
they boot a couple of different times in the PXE process before the OS
is laid down - and that during this dual boot process - they're getting
different IP addresses from the ISC daemon - even though they're sending
the same GUID each time (they acknowledge that the GUID is changing
after Windows is laid down).   From what I've read - this is not
expected behavior.  Can anyone validate please ?  I'm still awaiting
traces to see it for myself.

>>> Glenn Satchell <Glenn.Satchell at> 12/12/06 10:11 AM >>>

>Thank you for summarizing this.  Very helpful.
>With regards to differentiating the PXE boot, how would one do so ?

The easiest way would be with a class, eg:

class "pxe-clients" {
 match if substring (option vendor-class-identifier, 0, 9)="PXEClient";
 max-lease-time 600;

You could also add any other PXE specific things into the class as well
such as next-server, tftp filenames, and so on.

Glenn Satchell     mailto:glenn.satchell at | Some days we are
Uniq Advances Pty Ltd | the flies;  some
PO Box 70 Paddington NSW Australia 2021              | days we  are the
tel:0409-458-580  tel:02-9380-6360  fax:02-9380-6416 | windscreens...

>>>> Simon Hobson <dhcp1 at> 12/11/2006 6:46 PM >>>
>>We have a remote site using PXE to image workstations.
>>What we're seeing is the initial PXE boot (with a certain uid) is
>>causing a lease to be written to the leases file as active.
>>After the image is laid down and the machine boots the second time,
>>machine sends another Discover using a different uid, getting a
>>different lease.
>>I understand this is correct behavior per RFC, but have read that
>>is widely acknowledged to be an implementation PIA.
>>What's fuzzy to me after searching the archives is what everyone
>>to be options currently to this dilemna for me.
>>I've heard of patches, but can't seem to find them...other options ?
>Options :
>1) Configure short lease times, at least for those leases acquired by 
>PXE boot - at least then they can be easily re-used.
>2) Allow enough IPs to allow for them and just accept it.
>3) Configure your clients so they all use the same ClientID. If one 
>of the OSs is Windows then you'll have to make the rest match that 
>(it's fixed at <hardware type>:<MAC address>).
>4) Wait till version 3.1 comes out that will have a config option to 
>change how the client is identified.
>5) Use the patches (no, I don't know where they are) that fill in the 
>ClientID with the value Windows uses if it is empty.
>6) Persuade Microsoft to change their DHCP Client ;-)
>This E-Mail has been scanned for viruses.

This E-Mail has been scanned for viruses.

More information about the dhcp-users mailing list