Windows 7 / Networking

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Using PXE

The Windows operating systems include a DHCP client that can configure the IP address and other TCP/IP settings of computers with an operating system already installed. However, it is also possible for a bare metal computer-that is, a computer with no operating system installed-to use DHCP.

The Preboot Execution Environment (PXE) is a feature built into many network interface adapters that enables them to connect to a DHCP server over the network and obtain TCP/IP client settings, even when there is no operating system on the computer. Administrators typically use this capability to automate the operating system deployment process on large fleets of workstations.

In addition to configuring the IP address and other TCP/IP client settings on the computer, the DHCP server can also supply the workstation with an option specifying the location of a boot file that the system can download and use to start the computer and initiate a Windows operating system installation. A PXE-equipped system downloads boot files using the Trivial File Transfer Protocol (TFTP), a simplified version of the FTP protocol that requires no authentication.

Windows Server 2012 includes a role called Windows Deployment Services (WDS), which enables administrators to manage image files that remote workstations can use to start up and install Windows. For a PXE adapter to access WDS images, the DHCP server on the network must have a custom PXEClient option (option 60) configured with the location of the WDS server on the network.

The PXE client on the workstation typically needs no configuration, except possibly for an alteration of the boot device order, so that the computer attempts a network boot before using the local devices.

In a properly configured WDS installation of Windows 8, the client operating system deployment process proceeds as follows:

1. The client computer starts and, finding no local boot device, attempts to perform a network boot.
2. The client computer connects to a DHCP server on the network, from which it obtains a DHCPOFFER message containing an IP address and other TCP/IP configuration parameters, plus the 060 PXEClient option, containing the name of a WDS server.
3. The client connects to the WDS server and is supplied with a boot image file, which it downloads using TFTP.
4. The client loads Windows PE and the WDS client from the boot image file onto a RAM disk (a virtual disk created out of system memory) and displays a boot menu containing a list of the install images available from the WDS server.
5. The user on the client computer selects an install image from the boot menu, and the operating system installation process begins. From this point, the setup process proceeds just like a manual installation.