How to capture only TCP packets with tcpdump?

Last update: 27/12/2023
Author: Sebastian Vidal

If you are looking to filter only TCP packets when using the network traffic analysis tool tcpdump, You are in the right place. Sometimes debugging network traffic can be overwhelming, but with the right knowledge, you can simplify the process. In this article, I will guide you through the steps to capture only TCP packets with tcpdump and make the most of this powerful tool. Don't worry, it's not as complicated as it seems!

– Step by step ➡️ How to capture only TCP packets with tcpdump?

  • First, open your terminal or command line on your operating system.
  • Next, type the command tcpdump -i eth0 'tcp' and press Enter. This will capture only TCP packets on the specified network interface (in this case, "eth0").
  • Then, if you want to save the output to a file, you can add -w filename.pcap at the end of the command, where “file_name” is the name you want to give the capture file.
  • After, you can stop capturing at any time by pressing Ctrl + C.
  • Finally, to view the content of the capture file, you can use the command tcpdump -r filename.pcap. This will allow you to analyze the captured TCP packets.
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How to capture only TCP packets with tcpdump?

Q&A

Frequently Asked Questions about tcpdump and TCP packet capture

What is the syntax to capture only TCP packets with tcpdump?

The syntax to capture only TCP packets with tcpdump is:
1. Open the terminal.
2. Type the command tcpdump -i tcp interface.
3. Press Enter.

How do I filter TCP packets with tcpdump?

To filter TCP packets with tcpdump:
1. Open the terminal.
2. Type the command tcpdump tcp.
3. Press Enter.

How can I capture only TCP packets from a specific host with tcpdump?

To capture only TCP packets from a specific host with tcpdump:
1. Open the terminal.
2. Type the command tcpdump host [IP address] and tcp.
3. Press Enter.

Is it possible to capture only TCP packets on a specific port with tcpdump?

Yes, it is possible to capture only TCP packets on a specific port with tcpdump:
1. Open the terminal.
2. Type the command tcpdump tcp port [port number].
3. Press Enter.

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Can I use tcpdump to capture TCP packets from a specific network?

Yes, you can use tcpdump to capture TCP packets from a specific network:
1. Open the terminal.
2. Type the command tcpdump net [network address] and tcp.
3. Press Enter.

How can I view TCP traffic captured with tcpdump?

To view TCP traffic captured with tcpdump:
1. Open the terminal.
2. Type the command tcpdump -qtn -r [capture file name].
3. Press Enter.

What does the tcpdump -i any tcp command mean?

The tcpdump -i any tcp command means that TCP packets will be captured on all available network interfaces.

Can I capture TCP and UDP packets simultaneously with tcpdump?

Yes, you can capture TCP and UDP packets simultaneously with tcpdump:
1. Open the terminal.
2. Type the command tcpdump udp or tcp.
3. Press Enter.

How do I stop capturing TCP packets with tcpdump?

To stop capturing TCP packets with tcpdump:
1. Open the terminal.
2. Press Ctrl + C.
3. tcpdump will stop capturing packets.

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Where can I find more information about using tcpdump to capture TCP packets?

You can find more information about using tcpdump to capture TCP packets in the official tcpdump documentation or in online tutorials.