Computer Networking · Beginner level

Beginner level · Module 3: Basic Network Troubleshooting · Lesson 1 of 3

The Ping Ladder

Test connectivity step by step from your own device to the internet.

In this lesson you will

  • Use ping to test connectivity
  • Locate where a connection fails

Key concepts

pingloopbackdefault gatewayinternet address test

The lesson

Work outwards: ping 127.0.0.1 (the device's own network software), then your own IP, then the default gateway, then a known internet address such as 8.8.8.8, then a name such as example.com.

The first step that fails shows where the problem is: no reply from the gateway points to the local network; a reply from 8.8.8.8 but not from a name points to DNS.

Some devices block ping, so confirm a failure with another test before concluding.

Step by step

  1. Ping the loopback address.
  2. Ping the gateway.
  3. Ping an internet address.
  4. Ping a name and interpret results.
Troubleshooting tree

The ping ladder: where does the connection fail?

Testing outwards from your own device to find which part of the path is broken.

Does ping 127.0.0.1 (loopback) reply?
  • Yes
    Does ping to the default gateway (for example 192.168.1.1) reply?
    • Yes
      Does ping 8.8.8.8 (an internet address) reply?
      • Yes
        If ping example.com fails, DNS is the problem: check the DNS servers with ipconfig /all and test with nslookup.
      • No
        The router's internet link is down: check the WAN lights and the ISP status before changing settings.
    • No
      Local network problem: check the cable or Wi-Fi connection and run ipconfig. A 169.254 address means DHCP failed.
  • No
    The device's network software is faulty. Restart, then reset the network settings or reinstall the adapter driver.

Notes

Some devices block ping. Confirm a failure with another test, such as opening the router's admin page, before concluding.

Practice activity

Use the ping ladder on the lab faults and record where each fails.

Expected result: A record of tests showing where each connection fails.

Check your understanding

  1. If you can ping 8.8.8.8 but not example.com, what is likely wrong?

    Show answer

    DNS.

  2. What does failing to ping the default gateway suggest?

    Show answer

    A local network problem.

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