A PXE referral (also known as a net

A PXE referral (also known as a network boot referral) is the term for when a client is directed to download an NBP from a server other than the one it was in communication with through Dynamic Host Control Protocol (DHCP). This referral may be initiated by either a network boot server or a DHCP server. The following diagram shows the PXE referral process for a sample Windows Deployment Services configuration within a large organization.As illustrated in this diagram, a new client sends a PXE request. This request is answered by the active Windows Deployment Services server (WDS referral server in this diagram). Clients that have been prestaged in Active Directory Domain Services (AD DS) will be answered by this PXE server. WDS referral server checks AD DS to verify whether a computer account object exists for this client. This check reveals that the client was prestaged, and a property in the computer account indicates that the client’s referral server is WDS server 3. At this point, WDS referral server passes the request on to WDS server 3 , using the DHCPREQUEST packet. The client then begins the Trivial File Transfer Protocol (TFTP) download of the NBP from WDS server 3. Note that in the network design of this diagram, the only purpose of PXE referral servers 1, 2, and 3 is to provide images of the operating system. These servers do not respond to initial client service requests. Rather, WDS referral server services all PXE requests, checks AD DS for the existence of a prestaged computer account object, and then refers the client to the specified Windows Deployment Services server.