There is a feature on Cisco switches called “DHCP Snooping”.  This feature seems to break Netbooting from OS X servers.  The Netboot image will advertise on your network but you will not be able to boot from it.  To solve the problem you need to Trust DHCP Snooping on the Cisco port that the OS X Netboot server is plugged into.

On a Cisco switch, the commands should be similar to what’s shown below:

Myswitch(config)#interface GigabitEthernet3/47

Myswitch(config-if)#ip dhcp snooping trust

If you’re having this issue and your NOT using Cisco switches, check your switch manual to see if DHCP Snooping is supported and disable it on the switch port that your OS X server is plugged in to.