The following error is reported when running tcpdump command on NetScaler:

nstcpdump.sh <-- Command to start tcpdump from shell 
“bad dump file format”  <-- error message after executing above command

Please run below command from shell to stop already running tcpdump on netscaler and then start a new one to resolve the issue:

# nstcpdump -stop
 

Problem Cause

This issue will happen when we forget to turn off previous running tcpdump and then trying to start again not knowing that nstcpdump is already running.