Last updated: Apr 30, 2026
Network Diagnostic Tools
A few diagnostic tools that help to check whether a host is reachable, how traffic travels through the network, which ports are open, how DNS resolves, and what response a server returns.
Commands
ping - check if a host is reachable
ping sends small packets to a host and waits for a reply. It is useful for checking basic connectivity, for example when you are not sure whether the problem is with the network, browser, or application.
ping -c 4 8.8.8.8
ping google.com
ping6 2606:4700:4700::1111traceroute - show the route to a host
traceroute shows the network hops between your machine and the destination. It helps to debug where a connection slows down or fails.
traceroute google.com On Windows the command is tracert.
netstat - inspect network connections
netstat netstat shows your active network connections, listening ports, and routing information.
nslookup - query DNS records
nslookup checks how a domain name resolves to an IP address. Useful for simple DNS debugging.
nslookup google.comdig - detailed DNS lookup
dig is a more detailed DNS diagnostic tool. It can query specific record types, such as A, AAAA, MX, TXT, or CNAME
dig google.comcurl - make HTTP requests from the terminal
curl sends requests to URLs and prints the response. It is useful for checking APIs, headers, redirects, and server responses.
curl google.com
curl -I google.com # show only response headers
curl -L google.com # follow redirects
curl -X POST google.com -H "Content-Type: application/json" -d '{"name": "John"}' # send a POST request with JSON body