I intended to net-boot a DECstation 5000/20, in order to install NetBSD,
but I will only get this message:

KN02-CA V2.0m    (PC: 0xbfc00c78, SP: 0x801fffe8)
Boot: 3/rz0/vmunix
open(3/rz0/vmunix) failed: 19
Can't boot '3/rz0/vmunix'


This will be repeated continuously, without any boot-prompt visible...
What could be wrong? 


Thanks for any help.

/Henrik