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HI,

I am trying to set a capture filter to capture only DHCP packets and also a display filter for the same.

I know we can use -f option with tshark for capture filter and normally DHCP packets come on port 67 or port 68. I apply the same capture filter in wireshark GUI and it captures fine.

But when i try through Command Prompt its gives wrong syntax errors command: tshark -i 2 -f "port 67 or port 68" -R "bootp" -w capture.pcap

please help I am trying for a long time

asked 10 Oct '13, 23:07

Koushik%20Ganesh%20M's gravatar image

Koushik Gane...
11112
accept rate: 0%


What version are you running, on what OS, and what exactly is the error. On the version I have currently (I'm a bit lazy and haven't updated for a while from 1.9.2 development version), I get the following error.

./tshark.exe -n -i 3 -f "port 67 or port 68" -R "bootp" -w capture.pcap tshark: Read filters aren't supported when capturing and saving the captured packets.

This error isn't so much a syntax issue in that you can't use BOTH capture and read (the equivalent of Wireshark display filters) at the same time if you are saving the file.

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answered 11 Oct '13, 02:59

martyvis's gravatar image

martyvis
8911525
accept rate: 7%

I am running on windows 7 OS and the wireshark version is - Version 1.2.8 (SVN Rev 32676)

even trying with the normal capture filter syntax which is like: tshark -i 2 -f "port 67 or port 68" -w capture.pcap

does not work !! is the qoutes correctly given. do i need to change anything in the command ?

(25 Oct '13, 18:59) Gourab Majumdar

When you write, "does not work!!", what exactly do you mean? The command fails or you fail to capture DHCP traffic?

Perhaps you could provide answers to:

  • Are you sure you've specified the correct interface number? You can use tshark.exe -D to verify.
  • What is the exact output when you run that command, tshark -i 2 -f "port 67 or port 68" -w capture.pcap?
(26 Oct '13, 11:58) cmaynard ♦♦

tshark -i 5 -2 -R "http" -w test.pcap

tshark: Read filters aren't supported when capturing and saving the captured packets.

and

tshark -i 5 -Y "http" -w test.pcap

tshark: Display filters aren't supported when capturing and saving the captured packets.

Are both expected behaviors. This is "Bug 2234" as explained at:

https://bugs.wireshark.org/bugzilla/show_bug.cgi?id=2234

You can capture to a file, then use a capture filter with tshark and direct your output to a new file using tshark.

I also just successfully used the following (using v1.10.2)

dumpcap -i 5 -w - | tshark -r - -Y "http" -w file.pcap

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answered 26 Oct '13, 09:56

kpalmgren's gravatar image

kpalmgren
1446
accept rate: 0%

edited 26 Oct '13, 10:10

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question asked: 10 Oct '13, 23:07

question was seen: 7,128 times

last updated: 26 Oct '13, 11:59

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