Modern Linux networking work is usually built around the ip, ss, ping, traceroute, and DNS lookup tools. Older commands such as ifconfig, route, and netstat may still be available but are no longer the preferred defaults on many distributions.
Interfaces and addresses
ip addr ip link
Routing
ip route
Listening sockets
ss -tulpn
Connectivity and path
ping host traceroute host
DNS
host example.com dig example.com
For troubleshooting, start with the interface state, then verify routes, DNS resolution, and listening services before moving further up the stack.