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Difficulty: EasyWired and Wireless Network Issues

A desktop computer in an office environment suddenly loses network connectivity. Sequence the following troubleshooting actions in the correct bottom-up order, starting with physical layer verification and ending with remote network testing.

  1. 1Inspect the Ethernet cable connection and verify that the link lights on the network interface card (NIC) are illuminated.
  2. 2Run the `ipconfig /all` command to verify whether the computer has a valid IP address or an APIPA address.
  3. 3Ping the local loopback address (127.0.0.1127.0.0.1) to confirm that the local TCP/IP protocol stack is functioning properly.
  4. 4Ping the default gateway IP address to test connectivity within the local network segment.

Answer

The correct troubleshooting sequence starts with inspecting physical cable connections and NIC link lights, followed by checking IP configuration using ipconfig, testing the TCP/IP stack via loopback ping, and finally pinging the default gateway.
Following the CompTIA OSI bottom-up troubleshooting methodology, a technician first verifies physical Layer 1 connectivity (checking cable connections and NIC status lights). Next, the technician verifies Layer 3 logical IP addressing using `ipconfig`. After addressing is checked, testing the loopback address (127.0.0.1127.0.0.1) verifies the internal network stack. Finally, pinging the default gateway checks local network connectivity beyond the local host.

Step-by-Step Solution

1
Verify physical connection integrity
Ensures Layer 1 physical link is active and cable is plugged in properly.
Troubleshooting should start at the physical layer to avoid diagnosing software issues when a cable is simply unplugged.
2
Check IP configuration with `ipconfig /all`
Determines if DHCP assigned a valid IP address or if the host self-assigned an APIPA address (169.254.x.x169.254.x.x).
Identifying the IP configuration status helps target whether DHCP or addressing is at fault.
3
Ping the loopback address (127.0.0.1127.0.0.1)
Confirms the network interface card software and TCP/IP protocol stack are working.
If loopback fails, the network stack or OS network drivers are corrupted.
4
Ping the default gateway
Confirms whether the local computer can communicate with the local router.
Verifies local network connectivity before attempting to reach external internet resources.

Key Concept

CompTIA Bottom-Up Network Troubleshooting Methodology
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Topics

Wired and Wireless Network Issues

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