Do you know that using a pipe (|) will buffer output? And do you know that tcpdump and grep buffers their output too? You will always miss information using "tcpdump | grep"! You may use the "-l" option to tcpdump to stop buffering output. But you'd better use the tcpdump option directly for good filtering. Eg: tcpdump -lni eth0 'tcp port (3306 or 389 or 3128)'
Thank you very much for the answer, I considered the tcpdump filter options veeeeery complicated, therefore I chose to use easier filtering methods. I didn't use tcpdump very intensively, that's why... Just for some superficial network testing.
I'll try to RTFM from now on :D -- --------------------------- Alexandru Stefan-Voicu Catalyst Semiconductor INC. Device testing department ---------------------------