Windows ignoring DHCPOFFER is broadcast

Jamie Savage jsavage at
Thu Mar 27 18:17:32 UTC 2008

   I have a situation where I have setup a subnet with DCHP Cisco router in this case with the subnet interface 
config'd with the IP-helper command pointing to a DHCP server on another 
subnet.   I fire up my XP-SP2 laptop which starts looking for an IP 
address.  The 'remote' DHCP server sees the DHCPdiscover come in and sends 
out a DHCPoffer which is broadcast out to the originating subnet.   My 
XP-SP2 machine sees the broadcast (which carries the laptops MAC address 
buried in the Bootstrap Protocol portion of the frame) but ignores does not send a DHCPrequest back.   However, when I plug a 
MAC (Leopard) laptop or a LINUX laptop into the same port....they 
negotiate a  DHCP address with no problem.   Now, when I plug my XP-SP2 
laptop into another subnet which also uses DHCP-relay but points to a 
different DHCP works fine!   However, in this case the 
DHCPoffer is unicast specifically to the laptops 
broadcast.  .   I would think that any client that sees a broadcast frame 
with their MAC in the Bootstrap Protocol should respond.   Should 
DHCPoffers be unicast or broadcast or both?? Can someone point me in a 
direction to start looking?....I'm not sure if this is a Windows issue, a 
DHCP server issue or some networking issue. 

.........thanks in advance............J

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 
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <>

More information about the dhcp-users mailing list