nero@in-design.com said:
> 18:33:08.600000 markus.sgi.net.1023 > 255.255.255.255.sunrpc: udp 96
> 18:33:08.620000 caligula.sgi.net.sunrpc > markus.sgi.net.1023: udp 68 
> [...]
> 18:33:32.980000 markus.sgi.net.1023 > 172.16.255.255.sunrpc: udp 96
> 18:33:33.970000 markus.sgi.net.1023 > 172.16.255.255.sunrpc: udp 96
> 18:33:35.970000 markus.sgi.net.1023 > 172.16.255.255.sunrpc: udp 96

So the "indirect-whoami" broadcasts are answered if sent with
the all-one broadcast-address, but not if sent as network
broadcast (with the "natural" netmask).

It could well be that your server is broken.
To be sure, you could try to record the whole packet
("tcpdump -e -s 100 -xx udp port sunrpc" or so) or try
another server.

best regards
Matthias