override the client broadcast bit?

Carsten Strotmann (Men & Mice) carsten.strotmann at menandmice.com
Sat Sep 25 17:51:46 UTC 2010

Hash: SHA1

Hello David,

this blog post from the MS DHCP team gives some background why and how
they have changed the broadcast flag behavior in Windows 7:

"DHCP Broadcast flag handling in Windows 7"

Best regards

- -- 
Carsten Strotmann
Men & Mice Services
Address: Noatun 17, IS-105, Reykjavik, Iceland
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- ----- Original Message -----
> On Tue, Sep 07, 2010 at 12:05:03PM -0500, Marc Perea wrote:
> > Dhcpd clearly has no trouble honoring either a unicast or broadcast
> > response, so my question is: can we force the server to only respond
> > with a unicast, even if the client requested a broadcast response?
> > Getting new firmware on the modem may or may not pan out, but we're
> > also going down that road, FYI. Being able to force the server into
> > unicast mode would still be a useful tool though.
> Not currently. One concern is that if the client advertises the
> broadcast bit, it is advertising that it is not capable of receiving a
> directed unicast. So it would be unusual (but possible) for the
> parameter to actually help or work; although the packet may be
> delivered to the client, it may not be received.
> > Has anyone else had any experience with this - any tales to tell?
> New versions of Windows have suddenly started setting the broadcast
> bit to true. Older versions were quite capable of receiving
> directed unicasts when unconfigured, so this is a surprising
> de-evolution of their software, regressing to a state where it
> advertises a lesser capability. It's been reported that these Windows
> versions receive directed unicasts just fine even tho they have set
> the broadcast bit true.
> So there may already be a case for an 'always-unicast' configuration
> flag to oppose the 'always-broadcast' configuration flag.
> --
> David W. Hankins BIND 10 needs more DHCP voices.
> Software Engineer There just aren't enough in our heads.
> Internet Systems Consortium, Inc. http://bind10.isc.org/
> _______________________________________________
> dhcp-users mailing list
> dhcp-users at lists.isc.org
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