Network Troubleshooting: A Step-by-Step Guide to Fix Connectivity Issues

Key takeaways

• Work in order: link, IP address, gateway, internet by IP, DNS, application.
• The first failing test tells you where the fault is. Do not skip ahead.
• Change one thing at a time and note the result.
• Know the commands: ipconfig or ip addr, ping, traceroute or tracert, nslookup or dig.

What is the method?

Networks are layered, so faults are too. Test from the bottom up and stop at the first failure.

Step 1: physical and wireless link

Check cables, switch lights and Wi-Fi connection. On Linux, ip link shows each interface as UP or DOWN. A Wi-Fi device showing "connected" with no internet often points to the next steps, not the radio.

Step 2: IP address

ipconfig /all # Windows
ip addr # Linux

You want a valid address, mask and default gateway. An address starting with 169.254 on Windows means the device could not get an address from DHCP. Fix DHCP or check the cable and switch port.

Step 3: gateway

ping 192.168.1.1

Example output (illustrative):

64 bytes from 192.168.1.1: icmp_seq=1 ttl=64 time=1.8 ms

Replies mean the local network works. "Request timed out" or "Destination host unreachable" points to the local link, the wrong gateway or a switch problem.

Step 4: internet by IP

ping 8.8.8.8

If the gateway works but this fails, the fault is beyond your LAN: router, ISP or a blocking rule. If it works, your internet connection is fine.

Step 5: DNS

ping example.com
nslookup example.com

If pinging the IP works but the name does not resolve, DNS is the problem. The guide on fixing DNS issues covers cache flushing, resolver changes and DoH.

Step 6: path with traceroute

traceroute example.com # Linux
tracert example.com # Windows

It lists each router on the path with response times. A sudden run of timeouts or a jump in delay shows roughly where the problem lies. Some routers do not reply to traceroute, so asterisks alone do not prove a fault.

Step 7: application and firewall

If the network is fine but one service fails, check whether the service is listening and whether a firewall blocks it.

ss -tulpn # what is listening on this Linux host
nc -vz 192.168.1.20 443 # can I reach that port?

On Windows, Test-NetConnection host -Port 443 in PowerShell does the same check. See essential Linux networking commands for more.

Worked scenario

A laptop shows Wi-Fi connected but no websites load.

1. Interface is up.
2. ipconfig /all shows an address in the right range and a gateway.
3. Ping to the gateway works.
4. ping 8.8.8.8 works.
5. ping example.com fails to resolve.

Conclusion: connectivity is fine, DNS is failing. Switch the resolver or restart the router's DNS service, and the problem is solved at layer 5 of the checklist, not the radio.

Habits that save time

• Ask what changed recently.
• Compare with a working device on the same network.
• Change one thing at a time and write it down.
• Restart as a last resort, after you have collected evidence.

Next steps

For deeper practice, see CCNA troubleshooting scenarios and the CCNA 200-301 course or the Computer Network course. Packet capture with the Wireshark documentation is the next tool to learn.

Related reading

• What is the best way to track network latency and identify routing issues using tools like ping, traceroute, and MTR?
• What are the most common wireless network issues and how can you fix them?
• Recent CrowdStrike Update Triggers Blue Screen of Death (BSOD) on Windows, Affecting Numerous Users