The platform is a Dell PowerEdge 2400 running RedHat 6.2
The NIC seems to be Intel 82557-based.
The tcpdump that comes with RedHat 6.2 is not able to catch
packets other than broadcasts and packets directed at this server,
sniffing packets directed at another machine on the same 100Mb hub
does not work.
This must be a bug, as tcpdump 3.4 from ftp.ee.lbl.gov
works nicely when compiled on this machine.
What happens if you add -p? The man page is incorrect wrto the behavior
of ANK tcpdump, and needs fixing IIRC.
Fixed (by updating man page) in tcpdump-3.4-22.