A network administrator is notified that a user cannot access resources on the network. The network administrator checks the physical connections to the workstation labeled User 3 and sees the Ethernet is properly connected. However, the network interface’s indicator lights are not blinking on either the computer or the switch. Which of the following Is the most likely cause?

The absence of indicator lights (link/activity lights) on both the network interface card (NIC) and the switch port signifies a problem at the Physical Layer (Layer 1) of the OSI model. This means no electrical signal is being successfully negotiated between the two devices. While a faulty cable or hardware could be the cause, an administratively shut down port is a very common and likely reason. When a network administrator disables a port on a managed switch (e.g., using a shutdown command), the port stops transmitting or receiving data, and the physical link is severed, causing the indicator lights to go out.

A. The switch failed: A complete switch failure would impact all connected devices, not just a single user as described in the scenario.
B. The default gateway is wrong: This is a Network Layer (Layer 3) configuration issue. It would prevent communication with other networks but would not affect the Physical Layer link, so the lights would be on.
D. The VLAN assignment is incorrect: This is a Data Link Layer (Layer 2) configuration error. An incorrect VLAN would isolate the user from the correct network segment, but the physical link would still be active, and the lights would be on. ---

1. Cisco Systems

Inc. (2023). Troubleshooting Switch Port and Interface Problems. In the section "Troubleshooting Port and Interface Problems

" Step 3 advises to "Check the Port Status on the Switch." It explicitly states: "If the port is in the administratively down state

the link does not come up... Use the no shutdown interface configuration mode command to enable the interface." This directly supports that a shutdown port results in a down link state with no active lights.

Source Document: Cisco Technical Support & Documentation

Document ID: 116136.

2. Kurose

J. F.

& Ross

K. W. (2021). Computer Networking: A Top-Down Approach (8th ed.). Pearson. In Chapter 1

Section 1.5

"Protocol Layers and Their Service Models

" the physical layer is defined as being "responsible for transporting the individual bits... from one node to the next." An administratively disabled port prevents this fundamental function

thus no link can be established.

3. Ousterhout

J. (2019). Lecture 3: Physical and Link Layers. CS 144: Introduction to Computer Networking

Stanford University. The lecture notes emphasize that the physical layer's job is to transmit bits. The absence of link lights is a primary indicator of a physical layer failure

which includes the port being powered off or administratively disabled.