I've been trying to get network booting working on the Pi, i'm using a 3B+ so this should work. The Pi is in it's own VLAN with DHCP running from a QNAP NAS in a seperate VLAN, the NAS is also running TFTP, the network switch has the appropriate IP Helper settings. I've confirmed that PXE booting is working using another computer which i'm able to boot from fine. When i try it with the Pi i get nothing on the screen, i can see the DHCP offer from the QNAP DHCP but the Pi never attempts to call the TFTP server.
I've tried this with a number of Pi's all are otherwise working fine if booted from an SD card, i've also tried with a 3B Version 2. I'm certain that PXE booting is working in this configuration as I can boot PXELinux just fine with another type of device it's just the Pi's that don't ever seem to try to talk to the TFTP server.
Any ideas would be welcome