Arpdump, what does it solve?

[BostonU SysMgr]

Not much, it just dumps out some of the info to aid in detective
work.

Mainly as a matter of personal experience I find that if two hosts
won't talk to each other over an ethernet a good first thing to
be able to check is whether or not they ARP'd, it just eliminates
most of the networking software as the culprit (ARP is very simple
and requires almost nothing much in the way of software to be
configured right except that the two hosts agree on the other's
IP address as specified in /etc/hosts and that the same ethernet
is to be used.) If they won't ARP and the tables look right, and
an ifconfig and/or netstat and/or telnet-to-a-working-host seems
right, then I can concentrate on the hardware.

If you ARP'd in the recent past and the right stuff is in the
ARP table, then the hardware was obviously working in the recent
past so either your problem is not hardware or very recently has
become so (someone tripped over a transceiver cable or something.)

It's just another little piece of information, the trick with
debugging most anything is being able to peel away as much as
you can first. You may need something else to solve your problem.
Sorry.

	-Barry Shein, Boston University