Windows Vista cannot obtain an IP address from certain routers or from certain non-Microsoft DHCP servers

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I recently had a need to prove that my home router was not the cause of some networking issues.  So, I pulled an older router out of the closet and hooked it up.  I quickly noticed that there was a problem.  My Windows XP machine could obtain an IP address, but my Windows Vista machine could not.  I replaced the old router with the original one, and both machines started working again.  However, I needed to get the OLD router to work, so I had to do some digging.

I quickly found KB 928233 (https://support.microsoft.com/kb/928233/en-us).  This article discusses a difference in the way that XP and Vista handle the DHCP BROADCAST flag.  In XP, this flag is disabled by default.  In Vista, however, it is enabled by default.  My old router couldn't properly handle this flag, so it wouldn't give my Vista box an IP address.  I followed the instructions in the KB article, and everything started working.

Later on, and for other reasons, I decided to purchase a newer router.  Just for fun, I decided to set Vista back to its default behavior.  Sure enough, Vista had no problem with the new router.  This problem seems to occur only with older routers that cannot process the BROADCAST flag.

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