Wireshark · Wireshark-users: [Wireshark-users] why Wiresharks works (and tcpdump doesn't)

[Rogelio <scubacuda@xxxxxxxxx>]

My question is not so much around Wireshark, but rather why I have to 
use Wireshark rather than use tcpdump to find an unknown address of a 
network device.

(i.e. Say I have a router, and someone gave the internal interface some 
stupid IP, such as 1.2.3.4.  If my laptop is on the same subnet, then 
the command "tcpdump -i eth0 arp") finds the IP okay.  But if it's not, 
then I don't see that IP.  When I start Wireshark, however, I see the IP 
of the network device fly by.)

Any pointers in the right direction would be greatly appreciated.