How to find MAC addresses on network?

[Smoot Carl-Mitchell]

On Thu, 2009-01-22 at 21:54 +0000, Chris G wrote: 
> Is there a (reasonably) straightforward way of finding the MAC
> addresses of systems (well, strictly, interfaces) on a network?
> 
> arping works for some but not all of my hardware, presumably some
> things (like my HP printer) don't respond to arping.  What can I use
> to find the MAC address of the printer?

Gee, I hope your printer responds to ARP requests.  If it does not, it
is broken.  A trick I have used is to ping the local network's IP
broadcast address and then peek at the ARP cache.  After that I can see
the MAC addresses of all the devices on the network. e.g.

sudo ping -b 192.168.128.255
arp -a

Do not do this on a production network or a large network or you might
get a call from the network admin. :-)
-- 
Smoot Carl-Mitchell
Computer Systems and
Network Consultant
smoot at tic.com
+1 480 922 7313
cell: +1 602 421 9005