DHCP server bad address issue

Question

Hi,
I'm having an issue with ip address conflict or "bad_address"
I've checked for rogue dhcp server with wireshark. One issue i'm having is that the mac address of the device getting the bad_address issue on the dhcp server is only 8 characters. There is no such device like that on my network. This would be occuring every
other week. Removing it solved the problem, but how do i find the culprit of this problem?
Thanks.

Answer 1

What confuses me, is that it works fine at one site with all of your Windows 7 machines, but not the other. So something up with the DHCP Server? As I asked before, is it multihomed? If RRAS is installe on it, that constitutes multihoming, too.
OTH, Windows 7/Vista's DHCP Lease behavior is a bit different than XP. And keep in mind, we can't discount server side issues, yet, or we can look at this as a combo of the facts. In addition, if anything is on a VLAN, then that's another layer of "something"
else that we need to look at.
Anyway, here are my notes on Windwos 7/Vista DHCP lease behavior differences:
Windows 7 DHCP Lease Behavior is different than Windows XP upon startup
DHCP Client Behavior
http://blogs.technet.com/b/networking/archive/2009/01/29/dhcp-client-behavior.aspx
If the DHCP client obtained a lease from a DHCP server on a previous occasion, and the lease is still valid (not expired) at system startup, the client tries to renew its lease. 
If, during the renewal attempt, the client fails to locate any DHCP server, it attempts to ping the default gateway listed in the lease, and proceeds in one of the following ways:
•If the ping is successful, the DHCP client assumes that it is still located on the same network where it obtained its current lease, and continues to use the lease as long as the lease is still valid.  By default the client then attempts, in the background,
to renew its lease when 50 percent of its assigned lease time has expired.
•If the ping fails, the DHCP client assumes that it has been moved to a network where a DHCP server is not available.  The client then auto-configures its IP address by using the settings on the Alternate Configuration tab.  When the client is auto-configured,
it attempts to locate a DHCP server and obtain a lease.
As a workaround, you can force a Windows Vista or Windows 7 DHCP client to keep the old DHCP lease by adding registry key “DontPingGateway” if connectivity fails, see the resolution in the KB article below:
Windows Vista does not keep its DHCP IP address if a DHCP server is not available (works for Windows 7, too):
http://support.microsoft.com/kb/958336
Ace Fekay
MVP, MCT, MCITP Enterprise Administrator, MCTS Windows 2008 & Exchange 2007 & Exchange 2010, Exchange 2010 Enterprise Administrator, MCSE & MCSA 2003/2000, MCSA Messaging 2003
Microsoft Certified Trainer
Microsoft MVP - Directory Services
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