When the boot session starts, the PXE firmware attempts to bring up an adapter network link (port). If it succeeds to bring up a connected link, the PXE firmware communicates with the DHCP server. The DHCP server assigns an IP address to the PXE client and provides it with the location of the boot program.
Preparing the DHCP Server in Linux
NVIDIA Networking Server-Side Documentation of Flexboot v3.7.400 & UEFI v14.34.12