Mac Network Trace

From Steve Hellyer:

here's how to capture a full  
packet network trace on Mac OS X....

Open up Terminal and type:

sudo tcpdump -K -i en1 -s 0 -w trace.dmp

The -K tells tcpdump not to  verify TCP checksums.  The “-i” specifies  
the network interface (make sure your capture wireless interface), the  
“-s 0” means to capture the entire packet, and “-w trace.dmp” means to  
write it out to a file called trace.dmp.  This file will end up on the  
root of you own home folder.

If your not sure the interface you can open up Network Utility in the  
utilities folder and you can see the various interface there.

Use control - C to quit the packet trace capture.  These files can get  
big rather quickly so I recommend .zip archiving them before sending  
them or coping to a server share.

Steve