Symptom
Some NetBoot and/or Network Installation images do not appear the first time you choose Manage > Set Network Startup.
Solution
If the NetBoot or Network Installation image does not appear, follow these steps:
1. Close the Set Network Startup window.
2. Go to another computer on the same subnet.
3. Using the Startup Disk preference pane at that computer, verify the image is available
4. At the ARD administration computer, select the Set Network Startup command again.
The desired NetBoot or Network Installation image should be available if it is properly enabled on your server.
For more information on NetBoot and Network Installation image behavior see these documents: