In brief, the PXE protocol operates as follows: The client computer initiates the protocol by broadcasting a DHCP Discover packet containing an extension that identifies the request as coming from a client computer that implements the PXE protocol. Assuming that a boot server implementing this extended protocol is available, the boot server sends an offer containing the IP address of the server that will service the client. The client uses Trivial File Transfer Protocol to download the executable file from the boot server. Finally, the client computer initiates execution of the downloaded image.
The initial phase of this protocol piggybacks on a subset of the DHCP messages to enable the client to discover a boot server (that is, a server that delivers executable files for new computer setup). The client computer may use the opportunity to obtain an IP address (which is the expected behavior) but is not required to do so.
The second phase of this protocol takes place between the client computer and a boot server and uses the DHCP message format as a convenient format for communication. This second phase is otherwise unrelated to the standard DHCP services. The next few pages outline the step-by-step process during PXE client computer initialization.
For more information on troubleshooting PXE boot-related issues in Windows Deployment Services running in Legacy or Mixed mode, see the Microsoft Support article Description of PXE Interaction Among PXE Client, DHCP, and RIS Server.
Review the following solutions for PXE boot issues:
· Disable Windows PE logging to SetupAPI.log as described in Disable Windows PE Logging in Windows Deployment Services.
· Ensure that DHCP is configured properly as described in Ensure the Proper DHCP Configuration.
· Improve the response times for assigning IP addresses to PXE client computers as described in Improve PXE IP Address Assignment Response Time.