DHCP, dual NIC, DHCP failure

From: Henry Markov (jnhblhr_at_yahoo.com)
Date: 02/24/05 

Date: Thu, 24 Feb 2005 16:41:05 -0500

With my target devices I've found there is about a 50% probability that dynamic
IP addresses are not obtained for at least 6 minutes. The devices are industry
standard Compact PCI blades (PICMG 2.16) that use an Intel dual port network
controller (82546EB). Many well known vendors including Kontron, Momentum, DTI
and others have the same blade architecture. With a basic remote boot load
containing only standard components except for the XPe NIC driver obtained from
the Intel support site, there is an apparent race that causes the target to
abandon the DHCP protocol about 50% of the time. The problem appears about
equally likely in SP1 and SP2.

I conducted many tests with a 2.0GHz Pentium-M blade supplied by DTI, a cPCI
backplane, and a Win2003 server that was both boot server and DHCP server. The
proper sequence of DHCP messages for the client to obtain an IP address is:
Client Server
------ ------
Discover
               Offer
Request
               Ack
It appears to me that the DHCP client runs independent threads to execute this
protocol for each interface. In about 1/2 the cases the protocol is abandoned
by the client after a server offer. When the protocol is abandoned, it is
always abandoned for both interfaces. The client then restarts the protocol 5
to 6 minutes later and it typically succeeds for both interfaces however I have
seen one case where it failed on the second attempt and in this case the target
had no IP addresses for 14 minutes after boot.

Note that in a PXE boot scenario a DHCP address is obtained for an interface
twice -- once by the PXE BIOS client and once when the downloaded OS takes
control. DHCP never fails when executed under PXE, it only fails when executed
under XPe.

My client has just ordered $800,000 worth of equipment including 224 of the CPU
blades that I have tested. It is completely unacceptable that it can take 6
minutes or more for these blades to be network enabled after a boot. I really
need help on this one.

TIA,
Henry

Relevant Pages

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