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Network troubleshooting: the essential commands on Windows, Linux and macOS

The five-step method and the equivalent commands on all three systems to find where things break.

Networking Guide Intermediate Published October 14, 2026 Translated October 27, 2026 5 min read Version française
Router sitting on a table
Photo: Compare Fibre on Unsplash

In plain words

Troubleshooting a network is like finding out why no water comes out of the tap: you check the tap first, then the house meter, then the street, and finally the water plant. The first place where the water stops is where the fault is. The commands in this guide are your measuring tools at each step.

"The internet is down" can hide ten different causes. The method is to work outwards, from the nearest to the farthest: your machine, your network, the gateway, the internet, then the domain name. The first test that fails points to the culprit.

The five-step method

  1. Does my machine have an IP address? If not: cable, Wi-Fi or DHCP.
  2. Can I reach my gateway (the internet box, the router)? If not: local network.
  3. Can I reach an IP address on the internet? (9.9.9.9, 1.1.1.1) If not: the box or the internet provider.
  4. Does name resolution work? If the IP answers but not the name: DNS.
  5. Does the target service answer on its port? If everything else works: firewall or stopped service.

Tip

An address in 169.254.x.x (Windows, macOS) means the machine got no answer from the DHCP server.

The equivalent commands

Need Windows (PowerShell / cmd) Linux macOS
Show your IP address ipconfig /all ip -c a ifconfig or ipconfig getifaddr en0
Show the gateway ipconfig (Default Gateway) ip route route -n get default
Test reachability ping 192.168.1.1 ping -c 4 192.168.1.1 ping -c 4 192.168.1.1
Trace the path tracert 9.9.9.9 tracepath 9.9.9.9 or traceroute traceroute 9.9.9.9
Path + packet loss pathping 9.9.9.9 mtr 9.9.9.9 mtr 9.9.9.9 (Homebrew)
Query DNS nslookup example.com or Resolve-DnsName example.com dig example.com or resolvectl query example.com dig example.com
Test a TCP port Test-NetConnection example.com -Port 443 nc -zv example.com 443 nc -zv example.com 443
Local listening ports netstat -ano or Get-NetTCPConnection -State Listen ss -tulpn lsof -nP -iTCP -sTCP:LISTEN
Flush the DNS cache ipconfig /flushdns resolvectl flush-caches sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder
Renew the DHCP lease ipconfig /release then ipconfig /renew sudo nmcli con down <name> && sudo nmcli con up <name> sudo ipconfig set en0 DHCP

Reading the results

ping gets no answer, but the service works

Many servers and firewalls block ping (ICMP). A ping with no answer does not prove a machine is off: test the service port instead.

The name fails, the IP works

The problem is DNS. Compare with another DNS server:

dig @9.9.9.9 example.com          # Linux / macOS
nslookup example.com 9.9.9.9      # Windows

If it works with another server, the DNS handed out by your box or network is at fault.

traceroute shows stars

* * * lines in the middle of the path are normal: some routers do not answer these probes. What matters is whether the final destination is reached.

A port is "refused" or "timed out"

  • Connection refused: the machine is reachable but nothing listens on that port.
  • Timed out: a firewall is probably blocking the traffic somewhere.

Going further

  • mtr combines ping and traceroute continuously: ideal for spotting intermittent packet loss.
  • On Windows, Test-NetConnection 9.9.9.9 -TraceRoute gives the same path as tracert, with output you can use in a PowerShell script.
  • A ping to an IPv6 address (ping -6 on Windows, ping6 or ping on Linux depending on the version) helps spot an IPv6-specific problem.

Sources

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