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Getting started with tcpdump

Terminal - Getting started with tcpdump
tcpdump -nli eth0; tcpdump -nli eth0 src or dst w.x.y.z; tcpdump -nli eth0 port 80; tcpdump -nli eth0 proto udp
2009-02-05 17:41:55
User: jonty
Functions: tcpdump
2
Getting started with tcpdump

At some point you want to know what packets are flowing on your network. Use tcpdump for this. The man page is obtuse, to say the least, so here are some simple commands to get you started.

-n means show IP numbers and don't try to translate them to names.

-l means write a line as soon as it is ready.

-i eth0 means trace the packets flowing through the first ethernet interface.

src or dst w.x.y.z traces only packets going to or from IP address w.x.y.z.

port 80 traces only packets for HTTP.

proto udp traces only packets for UDP protocol.

Once you are happy with each option combine them with 'and' 'or' 'not' to get the effects you want.

Alternatives

There are 3 alternatives - vote for the best!

Terminal - Alternatives

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