Troubleshooting a Network
Use a systematic path from local interface to application.
Diagnose in stages
Check that the interface is connected and has a plausible address, mask, gateway and DNS resolver. Test the gateway, then a reachable remote IP, then a hostname. If IP connectivity works but names fail, investigate DNS. If a hostname resolves but the app fails, check ports, TLS and application responses.
A failed ping alone does not prove a host is down: ICMP may be blocked while HTTP still works.
Practical tools
ipconfig or ip addr shows interface settings. ping probes reachability where ICMP is permitted. traceroute or tracert explores responding hops. nslookup or dig inspects DNS answers. curl -I https://example.com checks HTTP response headers; adapt commands to your operating system.
Share results and timestamps when asking for help, but avoid publishing private IP plans, credentials or session cookies.
Check your understanding
DNS lookup fails, but an IP address is reachable. Where should you investigate first?