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Help with TCPDump commands.

Posted on 2009-02-23
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Last Modified: 2013-12-23
Dear experts,

I would like to use tcpdump to capture all the traffic between my pc and the target host.

I know that the tcpdump it will capture all traffic from the source that I will specify such as eth0

The question: I want the tcpdump to go and connect to target host and save all packets that received from the host in a file for a further analysis ? Can I do that with tcpdump or the tcpdump can not go and interact with target host ?

If the tcpdump can not go and interact with other hosts, what is the best way to do that interaction with target hosts and then save all packets between us and hosts.

I will be happy for any answers and suggestions.
Thanks in advance.
Best regards.
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Question by:Tree_PRO
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deimark earned 2000 total points
ID: 23713699
In short, no, tcpdump will not do what you want.

tcpdump is a tool to monitor (save to file) the packets coming in and out of your interface(s).

What you can do, is start the capture for your specific traffic, use another console or application to generate the traffic.  Once complete, stop the tcpdump and then review the results.

An example would be as follows to capture all traffic going to and from host 192.168.1.10 on interface eth0 and send to a file called "dumpfile"

tcpdump -i eth0 host 192.168.1.10 > dumpfile
or
tcpdump -i eth0 host 192.168.1.10 -w dumpfile

A handy page for all tcpdump commands is:
http://www.tcpdump.org/tcpdump_man.html

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Author Comment

by:Tree_PRO
ID: 23713759
Dear deimark,

Thanks for the reply, useful and short.

In this sitation, I would use another tool to interact with the host, the work will be like this:
1- run tcpdum and save all data to file
2- interact to host by another tool
3- stop tcpdump from capturing data.

About the point 3 , stop the tcpdump after finish from interact, is there any way to do that from the command line for example:
>tcpdump - (stop)

Or I have to stop it manually by control and C.


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LVL 18

Expert Comment

by:deimark
ID: 23713879
When you run tcpdump, it will run in the console session you started it from.  It will also give a live packet count to give you an idea if its working or not.

To stop it, I'm afraid the only way is to hit Ctrl-C as you said.

HTH
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Author Comment

by:Tree_PRO
ID: 23713901
Thanks man for helping me :)

Regards.
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