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 192.168.0.3 and net 192.168.0.253
port 80 or icmp
