ip command
in-depth look at ip address, link & route

netstat command
in-depth look at netstat and overview of its replacement ss

address resolution
in-depth look at nslookup, host, dig, arping & whois

host alive?
in-depth look at ping, ping6 & hping3

tracing routes
in-depth look at traceroute, tracepath & tracepath6

packet sniffing
in-depth look at tcpdump

swiss army knife
in-depth look at netcat

messaging local users

in-depth look at wall