Common tcpdump parameters

tcpdump is a useful tool for diagnosing network problems assuming you can understand it’s output. In order to understand it’s output it does help to filter the packets to be displayed down to those relevant. The -n flag is also useful for performance reasons, especially with hosts who’s ip’s do not resolve to names. My favourite filters for taming the output follow.

not port 22
net and net
port 80 or icmp