Wireshark-users: Re: [Wireshark-users] Complex Capture Filter Problem
Date: Fri, 14 Sep 2007 10:25:34 -0500


You might try using tshark with this as your one-line batch file.
It will display the amount of packets that have been captured meeting all
criteria and create a file, c:\dhcp.cap, that will have the information you
need.
It takes up very little memory

c:\progra~1\wireshark\tshark -t a -w c:\dhcp.cap -f "(port 67 or port 68)
and !(ether host  00:04:23:XX:XX:XX) and !(ether host  00:04:23:XX:XX:YY)"
-R "frame[282:3] == 35:01:02
or frame[282:3] == 35:01:05 or frame[282:3] == 35:01:06"

Ed Staszko
Network  Analyst
Mutual of Omaha
402-351-4272

"The Pleistocene Digital Hierarchy will revolutionize communication."  -
Frederick Flintstone


                                                                           
             "Travis Love"                                                 
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                                       [Wireshark-users] Complex Capture   
                                       Filter Problem                      
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I'm trying to create a capture filter to help detect rogue DHCP servers
with Wireshark.  So far, what I've come up with is a capture and a viewing
filter, each of which does half the work I need it to.  The capture filter
looks like:

(port 67 or port 68) and !(ether host  00:04:23:XX:XX:XX) and !(ether host
00:04:23:XX:XX:YY)

So it captures only DHCP packets that aren't to/from either of our DHCP
servers.  I then have to apply:

frame[282:3] == 35:01:02 or frame[282:3] == 35:01:05 or frame[282:3] ==
35:01:06

as a viewing filter in order to see only NAK, ACK, and DHCP OFFER packets.
Is there a way to put the viewing filter into the capture filter so my
box's RAM doesn't fill up with packets I'm not interested in?

Any ideas would be appreciated.  Thanks in advance,

Travis Love
Hope College CIT_______________________________________________
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