I have a 3/50 booting diskless, which gets to the second-stage boot:

>b le()                                    
Boot: le(0,0,0) 
Using IP Address 192.168.246.6 = C0A8F606
Booting from tftp server at 192.168.246.2 = C0A8F602
Downloaded 12600 bytes from tftp server.

>> NetBSD netboot [$Revision: 1.1.1.1 $]
Using IP Address 192.168.246.6 = C0A8F606
boot: client IP address: 192.168.246.6
boot: client name: nimrod2.bbn.com

and stops.  A tcpdump shows the client to be doing:

20:43:53.842793 arp-#25186 for proto #28516 (46) hardware #28018 (50)
20:43:57.842653 arp-#25186 for proto #28516 (46) hardware #28018 (50)
20:44:05.842516 arp-#25186 for proto #28516 (46) hardware #28018 (50)

What on Earth is going on?