Is the compute node BIOS configured for PXE boot?
If the compute node is properly configured for PXE boot, you should see words like PXE Network Boot, Boot Agent PXE, or something similar in the first couple of lines that are displayed on the compute node. If you see that the compute node attempts to boot from a CD, DVD, or hard drive, or if it boots into an existing operating system, then PXE boot is either disabled, or it is not the first option. Verify in the configuration of the BIOS of the compute node that the computer will boot from the network adapter that is connected to the Private network, instead of booting from the local hard drive or another device, and that Pre-boot Execution Environment (PXE) boot is enabled for that network adapter. Consult the documentation for your hardware regarding how to enable PXE boot and configure the boot order so that PXE boot is the first option.