HP xw6400 Network Boot DHCP failure - no client DHCPREQUEST after server DHCPOFFER

Alex Bligh alex at alex.org.uk
Mon Sep 12 13:44:22 UTC 2011

--On 12 September 2011 23:16:19 +1000 Glenn Satchell 
<glenn.satchell at uniq.com.au> wrote:

> so, you're looking at two completely different dhcp clients. One is part
> of the operating system (windows, linux, etc) and the other is built in
> to the BIOS of the computer (usually PXE).
> Seeing that the broadcast address is not sent, I might guess that the PXE
> client is not requesting it, arguably a bug. I bet other dhcp servers
> always include this option, even when it is not explicitly requested.

We've had very strange behaviour with DHCP 4.2 and Dell ILO cards where
the MAC address concerned is assigned a fixed-address. What happens
is that the ILO boots up, appears to borrow the MAC address of
the card, DHCPs and successfully gets address X, and squirrels it away
somewhere (CMOS?). PXE and the OS then correctly DHCP, and get address
X again, and all is well. Then someone changes the fixed-address clause
to address Y. It then DHCP's for ILO, does a DHCPREQUEST for
X, and gets a NAK (fair enough). What then happens is that normal
PXE boot and OS DHCP fail (I think again with NAK) and don't recover
to use address Y. I gave up debugging this, having discovered the
answer is to turn off ILO DHCP on interfaces you don't need/want it.

Alex Bligh

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