Cisco Certified Support Technician (CCST) NetworkingNetwork AccessMedium
A network technician is troubleshooting a connectivity issue on a user's workstation. The workstation is connected via an Ethernet cable to a wall jack, which connects to a network switch. The link light on both the workstation's NIC and the switch port is off. Which of the following is the MOST likely cause of this issue?
- AA misconfigured VLAN on the switch.
- BA faulty Ethernet cable or port.
- CIncorrect IP addressing on the workstation.
- DDHCP server is unavailable.
Show answer & explanationAnswer & explanation
Correct answer: B. A faulty Ethernet cable or port.
If the link lights are off on both the network interface card (NIC) and the switch port, it indicates that a physical layer connection has not been established. This is most commonly caused by a faulty cable, a disconnected cable, or a problem with the physical port itself.
Why the other options are wrong
- A. A misconfigured VLAN would allow the link lights to illuminate but could prevent network access. It's a Layer 2 issue, not Layer 1.
- C. Incorrect IP addressing would not prevent the link lights from illuminating; it would cause connectivity issues at a higher layer.
- D. An unavailable DHCP server would prevent IP address assignment but would not affect the physical link light status.
Physical Layer Troubleshooting
The Physical Layer (Layer 1) deals with the physical connection between devices. Basic checks include cable integrity, port status, and power.
- Link lights indicate physical connection status.
- No link light usually points to a cable or port issue.
- Always start troubleshooting with the lowest layer of the OSI model.
Memory trick: Cable's Dead, Link's Gone, Check the Port, Get it On!