[Dnsmasq-discuss] Problems With Windows Vista

[Simon Kelley]

Jeremy M wrote:
> I've tried everything on this one, but can't figure out what's going 
> on.  I have a router with 4 internal network interfaces with 4 instances 
> of Dnsmasq 2.51 running independently on each one.  All systems on the 
> network get DHCP responses without problems, except for machines running 
> Windows Vista.  When running from the router, Vista will simply not 
> accept the DHCP response even though requests are all being logged 
> correctly.  I've tried connecting over wired, wireless (through a WAP) 
> and different network segments/interfaces, but Vista will not accept a 
> response from anywhere.
> 
> For wireless, I'm running DD-WRT (http://www.dd-wrt.com/site/index) in 
> wireless access point (WAP) mode, so having exhausted everything else, I 
> tried enabling Dnsmasq (running version 2.45) on the WAP as a last 
> resort and for some reason, that works fine with Vista.  I tried copying 
> the config exactly as on the router (with some interface tweaks), but it 
> won't work.  I'm still running DHCP off the WAP just for Vista, but 
> would prefer to run on the router to centralize services and keep access 
> logs.
> 
> I've gone as far as running a packet sniffer on the router, and it 
> appears to be sending responses, but for some reason, Vista just won't 
> accept them.
> 
> Any thoughts or suggestions on why Vista won't accept responses from one 
> running instance of Dnsmasq (running on router), but will from another 
> (running on WAP)?
> 
> 
> Regards,
> 
> Jeremy M.
> 

Well, I guess the obvious question is "are there any differences between 
the responses from dnsmasq 2.45 and dnsmasq 2.51" Wireshark works really 
well at decoding these things, but if you're not confident at 
interpreting what it tells you, feel free to send me packet captures 
off-list.

One thing to consider is that vista (unlike almost all other DHCP 
clients) demands that the DHCP server sends back all responses as 
broadcasts. Inappropriate firewall rules on the system running dnsmasq 
2.51 which block these broadcasts would give exactly the symptoms you 
are seeing.

Simon.