I have a Windows 7 RC client that cannot get an IP address from a Windows Server 2008 R2 DHCP server. It comes up with an autoconfigured (169.x) address. Renewing (ipconfig /renew) returns the message "unable to contact your DHCP server". Other clients on the same LAN segment running different operating systems have been able to obtain addresses from the same DHCP server without problem. The symptoms are similar to: http://social.technet.microsoft.com/Forums/en-CA/w7itpronetworking/thread/f4732d8e-645d-4c10-b72a-8f7c18b1fd0d Things I have already tried: - Disabled firewall on the client -- no change. - Disabled IPv6 on the adapter -- no change. - Applied a registry hack for ARP problems with SonicWall firewalls (there's one on the same LAN segment) -- no change. - Given the client a static IP address -- everything works. Any ideas? Rob

Have you tried capturing the traffic between the client and the DHCP server?http://www.microsoft.com/downloads/details.aspx?FamilyID=983b941d-06cb-4658-b7f6-3088333d062f&displaylang=enKerry Brown MS-MVP - Windows Desktop Experience

I guess if this doesn't sound like some known problem, that's a good idea. Thanks for the link, Rob

It appears that the Windows 7 RC client sends out a DHCP DISCOVER message. The DHCP server replies with a DHCP OFFER message and a reasonable IP address for the client. The client ignores the OFFER and sends out another DISCOVER. The server duly sends out another OFFER, which the client once again ignores. So DHCP traffic is getting from the client to the server, and the server is doing something that looks reasonable. Either the client is not receiving the return traffic, or it's getting the traffic and then not doing the right thing (which would be to send a DHCP REQUEST with the offered IP address, normally. As noted, the same client works fine with a statically configured IP address, so whatever the problem is, it doesn't affect all incoming network traffic to the client.

Did you do the capture on the server or the client? Maybe the client is notseeing the OFFER? Is the client seeing any broadcasts? Maybe a firewall issue? Kerry Brown MS-MVP - Windows Desktop Experience

First, I clicked on the wrong button to say Kerry Brown aswer is the good answer (sorry for the mistake)now, can it also been that you have enabled the acces control in the DHCP server where you can add the MAC addresses that are alowed to get an IP from the DHCP server?Did you also tried to turn off the windows firewall features? because you have 3 groups: domain, public and private profile . Maybe there is a rule who doesn't allow you to answer the offer message from the DHCP server.

Capture on the client indicates that the client never sees the OFFER sent out by the server: The capture shows the client's DISCOVER messages, but not the corresponding OFFERs. The behavior is the same with or without Windows Firewall enabled on the client. Thanks for taking the time to reply to these, I appreciate it. Rob

This shouldn't be the problem on a Microsoft DHCP server but try the followinghttp://blogs.technet.com/teamdhcp/archive/2009/02/12/dhcp-broadcast-flag-handling-in-windows-7.aspxBeyond that all I can think of is a driver problem. Do you see any other broadcast traffic on the Win7 computer?Kerry Brown MS-MVP - Windows Desktop Experience

The client is seeing other broadcast traffic, such as ARP requests from other clients. It is using the broadcast flags as described in the article you referenced -- first trying four times with broadcast flag 0, then four times with broadcast flag 1. I guess I will have to see if there is another driver version available -- this one evidently has a problem specifically with DHCP processing. Thanks again for your help on this, I much appreciate it. Rob