Microsoft KB Archive/887725

= Your DHCP server may assign the same IP address to a virtual machine and to a host computer when you use a wireless network adaptor and Virtual Server 2005 =

Article ID: 887725

Article Last Modified on 11/2/2007

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APPLIES TO


 * Microsoft Virtual Server 2005 Standard Edition

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SYMPTOMS
When you configure your virtual machine to use a wireless network adaptor, your Dynamic Host Configuration Protocol (DHCP) server may assign the same IP address to the virtual machine and to the host computer.



CAUSE
This issue may occur when the following conditions are true:
 * The DHCP server does not comply with the standard that is described in RFC 2131, &quot;Dynamic Host Configuration Protocol.&quot;
 * Your wireless network adaptor is based on the 802.11 wireless specification.

The 802.11 specification does not permit the transmission of a packet whose source address is not the source address of the physical network adaptor. Because of this restriction, the Virtual Server guest operating system sets the &quot;chaddr&quot; field of its DHCP messages to the media access control (MAC) address of the physical network adaptor. The Virtual Server guest operating system sets the &quot;client identifier&quot; field of its DHCP messages to the virtual MAC address.

A DHCP server that complies with the RFC 2131 standard can use the client identifier field to distinguish between the virtual machine and the host computer. A DHCP server that does not comply with the RFC 2131 standard may not recognize the client identifier field. Therefore, it cannot distinguish between the virtual machine and the host computer.

Note This issue does not occur when you use a wired network adaptor.



RESOLUTION
To resolve this issue, use a DHCP server that complies with the RFC 2131 standard.



WORKAROUND
To work around this issue, connect to your router or access point by using a network cable.

Additional query words: 802.11x Client Ethernet Address Client-Identifier

Keywords: kbtshoot kbprb KB887725

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