Vista doesn't ack dhcp offer

John Wobus jw354 at
Tue Sep 18 22:00:23 UTC 2007

On Sep 18, 2007, at 5:37 PM, Kevin Sullivan wrote:
> We had a similar looking problem with certain XP boxes at certain 
> times.  I don't know if this is the same problem, but:
> We found that XP would send DISCOVERs, which were relayed to our DHCP 
> server (ISC on NetBSD) by the Cisco router.  XP wouldn't like the 
> OFFERs it received from the server, so it would rebroadcast the 
> DISCOVER several times.  If after three tries it didn't get an OFFER 
> it liked, it would decide to take any OFFER.
> However, by the time it decided to take any OFFER, it had configured 
> the network interface from to 169.254.x.x.
> The OFFERs as relayed by the Cisco were sent to the local network 
> broadcast (x.x.x.255).  These could be received by Windows when it had 
> an address of, but not when it had 169.254.x.x.  So by the 
> time Windows was ready to listen to the correct answer, it could no 
> longer hear the answer.
> Our solution was to change the Cisco to always send relayed broadcast 
> DHCP packets to, never x.x.x.255.  I don't know 
> exactly how this was done, but I can found out if you'd like.  We have 
> not seen this problem again since we made the change.
> Hope this helps.
> Kevin Sullivan
> Pittsburgh Supercomputing Center

We had this exact same problem with the same solution.  The client's 
address mask used with the net prevented it from receiving 
packets to the directed broadcast address.  The "solution" (i.e. 
workaround) was in the Cisco routers we use to relay.  The affected 
clients were old Windows clients.

John Wobus
Cornell University

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