XP Does Not Accept DHCP Leases from new VLANs

  • Thread starter Thread starter Josh
  • Start date Start date
J

Josh

When moving between VLANs all of our XP machines will not
accept lease offers from the DHCP servers for the new
subnet. I see the request going out for the old IP, and I
see offers coming in from the DHCP servers with a new IP
address, but XP ignores them. The only way I can fix this
is to reboot the machine. A manual
ipconfig /release|renew does not solve the issue.

If I can write a script to remove the DHCP lease cache, I
would entertain doing that, but I think that this is a
bug in the functionality of the DHCP client.

Any thoughts?

Thanks,

Josh
 
HOW TO: Use the Alternate Configuration Feature for Multiple Network Connectivity in Windows XP
http://support.microsoft.com/default.aspx?scid=kb;en-us;283676&Product=winxp

DHCP Client May Fail to Obtain a DHCP-Assigned IP Address
http://support.microsoft.com/default.aspx?scid=kb;EN-US;167014

--
Carey Frisch
Microsoft MVP
Windows XP - Shell/User

Be Smart! Protect your PC!
http://www.microsoft.com/security/protect/

---------------------------------------------------------------------------------

"Josh" (e-mail address removed) wrote in message:

| When moving between VLANs all of our XP machines will not
| accept lease offers from the DHCP servers for the new
| subnet. I see the request going out for the old IP, and I
| see offers coming in from the DHCP servers with a new IP
| address, but XP ignores them. The only way I can fix this
| is to reboot the machine. A manual
| ipconfig /release|renew does not solve the issue.
|
| If I can write a script to remove the DHCP lease cache, I
| would entertain doing that, but I think that this is a
| bug in the functionality of the DHCP client.
|
| Any thoughts?
|
| Thanks,
|
| Josh
 
I would but the problem is more complicated than that.
The users need to roam between multiple VLANs (not just
two), each of which has its own DHCP scope. Using static
configuration is not an option (even as an alternate) for
numerous reasons.

When the client sends out the DHCPDISCOVER, it is
populating the CIADDR/"DHCP Option Field DHCP: Requested
Address" fields with the old IP address (this is normal).
The DHCP servers respond with a DHCPOFFER whch the client
ignores. However, because the scope which is
handling/sending the offer is not the same scope of the
old subnet address space, the DHCP server will not send a
NACK to have the client release the address. It appears
that this is by design (per the RFC).

So, it appears that the situation I have is that I need
to stop the client from populating the CIADDR/"DHCP
Option Field DHCP: Requested Address" fields with the old
IP.

Josh
-----Original Message-----
HOW TO: Use the Alternate Configuration Feature for
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Multiple Network Connectivity in Windows XP
 
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