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DHCP issues with PXE boot and Win7 OS streamed by Citrix
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Is anyone using Citrix to stream Windows 7 to workstations?
We’re running into some annoying hurdles in our pilot deployment. We’re using Dell 745 workstations with the hard drives removed and booting off the network. An Infoblox appliance is providing DNS/DHCP/TFTP services.
The device does a PXE boot and gets an IP address (188.8.131.52) and the boot file for the Citrix server from the Infoblox DHCP/TFTP server. Once the Windows 7 OS is loaded, it issues a DHCP request and the DHCP server responds with a second IP address (184.108.40.206).
On our Infoblox DHCP server, I’ve set the PXE DHCP lease times to 5min. However, if you run IPCONFIG on the Windows 7 system, you’ll see both IP addresses:
IPv4 Address. . . . : 220.127.116.11 (Preferred)
IPv4 Address. . . . : 18.104.22.168 (Deprecated)
What’s odd is after the 5min PXE lease time, the Windows 7 OS still has the Deprecated IP address active. While on the DHCP server, the lease status for that same IP address is “free” and it will attempt to offer that IP address again. (It fails to offer the IP address because the DHCP server issues a ping test before actually offering. I don’t know how much of a time delay this introduces in offering a DHCP address to a device. Wouldn’t think much.).
As a test, we assigned a fixed IP address to the MAC address of one of these workstations. When it booted, the PXE boot and the Win7 OS used the same IP address. So, we’re only using one IP address, but it’ll be additional overhead to manage if it changes networks.
So, the DHCP pool needs to be twice as large as the number of devices; however, we’d occasionally get the PXE-E51 error: “ No DHCP or proxyDHCP offers were received”. When we’d check the DHCP pool for that network, it would not be at 100% capacity.
I’m not sure where to start with this problem;
- How/why is the Win 7 OS picking up the IP address assigned to the PXE boot image? Is this a PXE or Win 7 problem?
- PXE devices don’t send a “UID” to the DHCP server but Windows does; so, the DHCP server treats these as separate requests. Is this a DHCP configuration problem since the workstation works when the same IP address is issued via DHCP based on the MAC address to both the PXE and Windows DHCP requests? From what I’ve read, the DHCP server is supposed to respond with a different DHCPOffer if the “UID” is different in the DHCP request.
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