Network, domains and routing

Send request to network host to trigger response (limit count via -c)

ping <domain>
ping -c <count> <host>

Show internet route to host

traceroute <host>

Protocols / Ports

Network protocol status (limit to specific protocol -p eg. tcp, udp)

netstat
netstat -p <protocol>

Show processes that are listening on ports

lsof -i -P | grep LISTEN

Check if specified port is open at IP address (macOS: -G <timeout> in seconds)

nc -zv -G <timeout> <ip-address> <port>

Domains

Show registration details for domain

whois <domain>

DNS Records

Show basic (and expanded using any) DNS records for domain (Note: any may be disabled by the DNS provider)

dig <domain>
dig <domain> any

Show specific DNS records for domain (eg. A, MX, NS)

dig <record-type> <domain>

Alternative DNS lookup utility to dig

host -a <domain>
nslookup -q=<record-type> <domain>

Name Servers

Show authoritative name servers for domain (+short for minimal output)

dig NS <domain>
dig +short NS <domain>

Alternative name server lookup utility to dig

host -t NS <domain>
nslookup -q=NS <domain>

Web Browsers

Clear stale DNS cache in chrome (Open Chrome DNS settings -> Clear host cache)

chrome://net-internals/#dns

Chrome Net Internals can also show the DNS entries for specific domains