[GLLUG] tcpdump

[Chick Tower]

I upgraded to the new Slackware (14.2), and it has a newer version of 
Firefox (45.3.0, after one upgrade).  I'm on dial-up, and as soon as I 
fire up Firefox the modem lights start flashing away, and my effective 
modem speed seems to be at least halved.  So, in addition to trying 
other, less "chatty" browsers, I wanted try and analyze the traffic to 
see if I could block it or modify Firefox to stop it.

Has anyone used tcpdump?  I was looking at wireshark, but it said it was 
a graphical version of tcpdump, and tcpdump is already installed. 
However, when I run it, even according to the examples, it doesn't catch 
anything at all.  I've tried the following commands, as root:

tcpdump host <myhostname>
tcpdump -v host <myhostname>
tcpdump -v host <myfullyqualifiedhostname>
tcpdump -v host localhost

Does anyone have any tips?
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                                Chick