What are the steps for a PXE client to get a boot image from a boot server?

Document ID : KB000054406
Last Modified Date : 14/02/2018
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Description:

This document outlines how a PXE machine to acquires an IP address and gets a boot image.

Solution:

  1. On power up, the target PXE client sends a DHCP discovery broadcast

  2. The boot server responds with an offer of the boot server's IP address

  3. The DHCP server responds with an offer of an IP address

  4. The PXE client requests an IP address from the DHCP server

  5. The DHCP server acknowledges the request and grants the IP address

  6. The PXE client requests a boot file (Note: It now has a valid IP address)

  7. The DHCP server acknowledges the request but does not know the location of the boot file

  8. The boot server acknowledges the request and details the location and name of the boot file to use

  9. The PXE client makes a TFTP (Trivial File Transfer Protocol) request for the boot file

  10. The boot server acknowledges the request and the boot file is transferred to the client via TFTP

For CISCO routers the following command should be used to configure the IP Helper:
IP helper-address <address of boot server>

In addition for WinPE bootimages, UDP packets should be forwarded over port 4011 with the following command:
IP forward-protocol UDP 4011