XP clients sometimes ignore DHCPOFFERs
MKing at bridgew.edu
Wed Mar 15 21:34:26 UTC 2006
> -----Original Message-----
> From: dhcp-users-bounce at isc.org
> [mailto:dhcp-users-bounce at isc.org] On Behalf Of Sebastian Hagedorn
> However, in contrast to the server in the article, the ISC
> server responds to all three of them with the same OFFER.
> When things go wrong the client just gives up after the third
> DHCPDISCOVER and assigns a link-local IP (169.x.x.x).
> We are told that this problem never occurs with other
> servers, e.g. those built into home DSL routers. All things
> being equal one would expect the
> *same* problem when those users return from work and plug
> their computers into their routers at home.
> We have sniffed the entire "conversation" between client and
> server using Ethereal on *both* the client and the server. To
> my eyes everything looks the way it should look. We would
> like to just blame Microsoft, but I can't find anything
> regarding this in the KnowledgeBase and, more importantly,
> something must be different if this never happens with those
> routers at home.
Actually, I think it's the home routers that are killing you. :-)
There is another Microsoft "Feature" you failed to mention:
If the DHCP client has previously obtained a lease from the DHCP server, the client tries to renew any unexpired lease with the DHCP server. If the client fails to locate any DHCP server, it attempts to ping the default gateway listed in the lease. If this succeeds, the client assumes it has not been moved and uses that lease. The client then seeks to automatically renew the lease when half of the lease time has expired.
If the attempt to ping the default gateway fails, the client assumes that it has been moved to a network that has no DHCP services currently available, such as a home network and it configures itself. It then automatically keeps trying to find a DHCP server every five minutes.
Can these clients / you ping 192.168.1.1 (or 192.168.0.1)? If you can, that's why they won't let go of they're IP and take a new one.
I had this problem for quite awhile. (Captive portal, answering to any address that would ping 192.168.1.1, and it was using 192.168.1.1 as it's "DHCP" Server address. We moved it to 10.255.255.1, and the problem went away)
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