CCNA Network Infrastructure and Connectivity Practice Question
A network technician replaced a faulty SFP transceiver on a switch port. After replacement, the port remains in a down/down state. The technician verifies the fiber cable is securely connected at both ends and observes that the remote switch port is also in a down/down state. What should the technician do next?
⚠ Common exam trap
Cisco often tests the distinction between physical layer issues (cable, SFP) and administrative state issues (shutdown), where candidates mistakenly focus on hardware compatibility or VLAN settings when the port is simply disabled via configuration.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Check the running configuration for the no shutdown command on the interface.
The most common cause of a port remaining in a down/down state after replacing a faulty SFP is that the interface is administratively down. The 'no shutdown' command must be applied to bring the interface up. Since the technician already verified physical connectivity and both ends show down/down, the issue is likely at the configuration layer, not the physical layer.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Verify that the speed and duplex settings are set to auto-negotiation.
Why it's wrong here
Checking speed/duplex is a layer-1/2 action, but it is not the immediate next step. Interface administrative status should be verified first because if the port is shut down, no speed or duplex negotiation occurs; this skips a more basic check.
- ✗
Check whether the SFP module type is incompatible with the switch.
Why it's wrong here
Although an incompatible SFP module can prevent a link from coming up, the stem states both local and remote ports are down/down, which indicates a Layer 1 issue such as a faulty cable, mismatched fibre type (single-mode vs. multi-mode), or a damaged transceiver. Checking compatibility is tempting because a mismatched SFP will indeed cause a port to remain down, but the technician has already verified the cable is securely connected and the remote port is also down, so the next step should be to test the fibre cable or swap the SFP with a known-working unit, not to check compatibility.
- ✗
Verify the VLAN assignment on the port.
Why it's wrong here
A wrong VLAN assignment affects traffic forwarding at Layer 2 but does not cause a link to be down. The down/down state indicates a Layer 1 problem, so checking VLANs is irrelevant to restoring the link.
- ✓
Check the running configuration for the no shutdown command on the interface.
Why this is correct
This is the most immediate and logical next step. A shut-down interface displays as down/down (or administratively down/down), and without verifying the administrative state, all other troubleshooting is premature. The technician has already addressed physical connectivity, so a configuration oversight must be ruled out.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
✓Check the running configuration for the no shutdown command on the interface.Correct answer▾
Why this is correct
This is the most immediate and logical next step. A shut-down interface displays as down/down (or administratively down/down), and without verifying the administrative state, all other troubleshooting is premature. The technician has already addressed physical connectivity, so a configuration oversight must be ruled out.
✗Verify that the speed and duplex settings are set to auto-negotiation.Wrong answer — click to see why▾
Why this is wrong here
Candidates assume a speed mismatch must be the problem due to the down/down state, overlooking that a shutdown interface also appears down/down (without the 'administratively' prefix in some outputs) and that the physical check was already done.
✗Check whether the SFP module type is incompatible with the switch.Wrong answer — click to see why▾
Why this is wrong here
The urgency to blame the newly installed hardware leads many to skip the quick-win config check, potentially wasting time on hardware replacement when the fix is a single command.
✗Verify the VLAN assignment on the port.Wrong answer — click to see why▾
Why this is wrong here
Candidates often confuse link status with connectivity issues that occur after the link is up, mistakenly targeting a Layer 2 problem for a Layer 1 symptom.
Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Quick reference
OSI Model Reference
| Layer | Name | PDU | Key Protocols / Devices |
|---|---|---|---|
| 7 | Application | Data | HTTP, HTTPS, DNS, SMTP, FTP, SSH |
| 6 | Presentation | Data | TLS / SSL, JPEG, ASCII encoding |
| 5 | Session | Data | NetBIOS, RPC, SIP |
| 4 | Transport | Segment / Datagram | TCP, UDP |
| 3 | Network | Packet | IP, ICMP, OSPF — Routers |
| 2 | Data Link | Frame | Ethernet, Wi-Fi, PPP — Switches, Bridges |
| 1 | Physical | Bits | Cables, NICs, Hubs, Repeaters |
Go deeper
Related to this question
Learn chapter
Network Topology Types
Key term
Switch
A switch is a networking device that connects devices on a local area network and uses MAC addresses to forward data only to the intended recipient.
Key term
Interface
An interface is a point of connection or interaction between two systems, devices, or software components that allows them to exchange information or signals.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 200-301 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 200-301 exam.