Code
linux
# Interfaces and addresses
ip addr show
ip -br link
ip route
ip -s link
# Port and connection inspection
ss -tlnp # TCP listening ports + process
ss -tnp state established
netstat -tulpn # legacy alternative
# Connectivity
ping -c 4 example.com
traceroute example.com
mtr -c 10 example.com
# DNS
dig +short example.com
nslookup example.com 8.8.8.8
getent hosts example.com
# Curl and HTTP debugging
curl -sI https://example.com
curl -w "@curl-format.txt" -o /dev/null -s https://example.com