• PXE stands for preboot execution environment, one of the most common network boot protocols. PXE works by using a combination of DHCP (dynamic host configuration protocol) and TFTP (trivial file transfer protocol) to download a network boot program (NBP) from a server to the client machine.
  • Other protocols related to network booting include BOOTP (bootstrap protocol), which is an older protocol that has largely been replaced by DHCP.

Network boot is the process of booting a computer from a network rather than a local drive. This method of booting can be used by routers, diskless workstations and centrally managed computers (thin clients) such as public computers at libraries and schools. In this blog, you can understand one of the most common network boot protocols, PXE and how it works.

What is preboot execution environment (PXE)

Preboot execution environment (PXE), pronounced pixie, is a set of standards that enables a computer to load an operating system (OS) over a network connection. It was introduced as part of the Wired for Management framework by Intel and is described in the specification published by Intel and SystemSoft. PXE can be used to quickly install an OS and is commonly used for both servers and clients. It may also be called PXE boot, boot from network, network boot or local area network boot.

It describes a standardised client–server environment that boots a software assembly, retrieved from a network, on PXE-enabled clients. On the client side it requires only a PXE-capable network interface controller (NIC), and uses a small set of industry-standard network protocols such as DHCP and TFTP.

The concept behind the PXE originated in the early days of protocols like BOOTP/DHCP/TFTP, and as of 2015 it forms part of the unified extensible firmware interface (UEFI) standard. In modern data centers, PXE is the most frequent choice for operating system booting, installation and deployment.

Also read: Firmware uncovered: Is it hardware, software, or both?

Also read: How to fix a slow internet connection?

How PXE works

PXE requires several standards for the client and server to successfully boot. The client must support PXE in unified extensible firmware interface (UEFI) or network interface card (NIC) firmware. The network must have a configured dynamic host configuration protocol (DHCP) server and a trivial file transfer protocol (TFTP) server. There is generally also another imaging server.

The DHCP server uses options 66 and 67 to advertise the PXE boot server internet protocol (IP) address. The client then contacts the boot server and downloads and boots the network bootstrap program (NBP) using TFTP. The NBP is a small OS that contains just a kernel, basic drivers and basic programs that can download the remaining OS components. Windows preinstallation environment or a small Linux OS are the most common OSes loaded by a network boot.

PXE acceptance since v2.1 has been ubiquitous. Today it is virtually impossible to find a network card without PXE firmware on it. The availability of inexpensive Gigabit Ethernet hardware has made PXE the fastest method available for installing an operating system on a client when competing against the classic CD, DVD, and USB flash drive alternatives.