Linux clients working, XP not.

Jamie Savage jsavage at
Fri Apr 11 17:15:21 UTC 2008

    I'm not sure if the situations are exactly the same but I had the same 
issue a few weeks ago.  MACs and LINUX obtained IPs with no problem but XP 
machines failed.  We have Cisco gear and I was using DHCP-relay.  The 
solution to my problem (and hopefully yours) was provided by David 
Hankins.   He advised the following;

'first thing to check; do you have 'ip broadcast-address' configured
on the first Cisco with the ip-helper set up?

Windows boxes, when they receive broadcasts, are very conservative in
what they receive; it MUST be sent to as dictated in
rfc2131, and cisco relays in this configuration will use the
configured broadcast address instead.'

In my case I had config'd an 'ip broadcast-address' statement on the 
router port.  This meant that the response went back to rather 

MACs and LINUX are happy seeing either response but Windows (as David 
pointed out) absolutely needs to see a broadcast to

.........hope this helps (with thanks to David 

James Savage                                   York University 
Senior Communications Tech.       108 Steacie Building
jsavage at                            4700 Keele Street
ph: 416-736-2100 ext. 22605            Toronto, Ontario
fax: 416-736-5701                                M3J 1P3, CANADA 

"Jeff Sumner" <Jeff.Sumner at> 
Sent by: dhcp-users-bounce at
04/11/2008 12:04 PM
Please respond to
dhcp-users at

dhcp-users at

Linux clients working, XP not.


Can someone point me to any documentation for troubleshooting why Linux
clients would work with a particular configuration from an implementation 
ISC DHCP but XP clients won't?

I see packets coming in and going out of the DHCP server via a sniffer, 
the XP clients won't send an ACK, where the Linux boxes will.

The XP clients don't get addresses.

I'm poking around Google, and see several instances of folks having 
with this, but no fixes are listed- the threads just die off. It seems 
sometimes XP reboots fix the trouble, but that's not helping here. Again,
Linux guests work fine, to the point of DDNS working extremely well.

Someone brought an XP workstation into the lab and suddenly, we have a
troubleshooting opportunity!

Server versions tried are DHCP3.1.1rc1, 3.1.0 and 3.0.6. Host is AIX 5.1 
built with GCC.

Network is private, 192.168.0. Many options defined, but nothing seems to
get the XP boxes to ACK.


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