BootP Flags in DHCPOFFER Packet

Benjamin Wiechman benw at
Mon Aug 27 17:16:10 UTC 2007

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I haven't seen this issue in the ISC dhcp server, but since there are many
people here who are deeply familiar with the RFC and behaviors I was curious
if someone could explain this to me. 


We are trying to enable NAT on some network devices and I am seeing this
issue (among others!)


When the device responds with a DHCPOFFER it isn't consistently setting the
bootp flags in the bootstrap protocol packet.


See the two wireshark captures to demonstrate this:


In one the bootp flags are set to broadcast - this packet is ignored by the
client (winxp in this case - running realtek card)

In the other the bootp flags are set to unicast - this packet is accepted
and processed by the client.


Is one of these a violation of the RFC, or is there some other reason the
first would be ignored by the client while the second is accepted?


Ben Wiechman

Wisper High Speed Internet

Office: 866.394.7737

Direct: 320.256.0184

Cell: 320.247.3224

ben at


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