TCPDump: Difference between revisions

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= Basics =
== TCPDump Filters==
 
* TCPDump done with "-i any" will result in packets with No Ethernet Headers captured in wireshark.
tcpdump -i eth0
 
* TCPDump uses libpcap which processes packets before they get processed by IPTables.
* Therefore TCPDump will see Incoming Ping packets though they are dropped by IPTables.
* TCPDump will see inbound traffic before iptables, but will see outbound traffic only after the firewall has processed it.
 
= Filters =
Source: [[http://www.thegeekstuff.com/2010/08/tcpdump-command-examples/ thegeekstuff.com]]
 
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<br />
 
=== Reading PCAPs ===
 
{| class="wikitable"
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=== TCPDump Parameters ===
 
==== Modifiers== ==
 
====Modifiers====
{| class="wikitable" style="width: 20%"
|-
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==== Examples== ==
 
{| class="wikitable"
! Filter !! Description
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==== Protocol keywords== ==
 
{| class="wikitable" style="width: 30%"
!colspan="3"|Keywords
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|}
 
==== TCP Flags== ==
 
{| class="wikitable" style="width: 30%"
!colspan="3"|Flag Keywords
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|}
 
==== Capture Filter Primitives== ==
 
{| class="wikitable"
|-
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=== Command Line Options== =
 
-A Print frame payload in ASCII
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<br />
 
=== AdvancedDocker Packet FilteringCaptures ===
docker exec -it 428947239426349 tcpdump -N -A 'port 80' -w capture.pcap
 
= Advanced Packet Filtering =
 
*List interesting traffic from all the PCAP files:
<syntaxhighlight lang='bash'>
<pre style="width: 2000px; overflow-x: scroll;">
for i in `find . -type f | egrep "All.pcap"`; do echo $i; tcpdump -r $i '((host 1.1.1.1 or host 2.2.2.2) and host 3.3.3.3) and port 445' ; echo -e "\n"; done
</syntaxhighlight>
</pre>
 
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