- A
Check the switch port’s VLAN configuration and ensure the host and router interface are in the same VLAN.
If the host and gateway are in different VLANs, the ARP request broadcast never reaches the gateway, so the entry stays incomplete. This step directly addresses the most probable Layer 2 fault after excluding physical issues.
- B
Replace the Ethernet cable between the host and the switch.
Why wrong: The technician has already verified the cable is connected and the switch port is active. Replacing the cable before investigating logical configuration is premature and unlikely to resolve a VLAN or ARP issue.
- C
Clear the ARP cache on the host and attempt to ping the gateway again.
Why wrong: Clearing the cache does not address the reason the ARP reply was not received. The entry will simply become incomplete again if the underlying problem (e.g., VLAN mismatch, gateway interface down) persists.
- D
Check the router’s routing table for a route to the host’s subnet.
Why wrong: The default gateway IP is the router’s own interface address; it does not need a route to respond to an ARP request. ARP resolution is a Layer 2 process for a directly connected network, not a routing decision.
Quick Answer
The correct next step is to check the switch port’s VLAN configuration and ensure the host and router interface are in the same VLAN. An incomplete ARP entry for the default gateway means the host sent an ARP request but never received a reply, and since the physical layer is verified as operational, the root cause is almost always a Layer 2 mismatch. When the host and router interface reside in different VLANs, they are in separate broadcast domains, so the ARP reply cannot reach the host, leaving the entry stuck in an incomplete state. On the CCNA 200-301 v2 exam, this scenario tests your ability to isolate Layer 2 issues from Layer 3 problems—a common trap is to immediately suspect IP addressing or routing, but the incomplete ARP points directly to a VLAN mismatch or misconfigured access port. Remember the memory tip: “ARP incomplete? Check the VLAN—same broadcast domain or the reply won’t come.”
CCNA Network Infrastructure and Connectivity Practice Question
This 200-301 practice question tests your understanding of network infrastructure and connectivity. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A host cannot communicate with its default gateway. The technician uses the show arp command on the host and sees that the ARP entry for the gateway IP is incomplete. The technician has already verified that the Ethernet cable is securely connected and the switch port is active. What should the technician do next?
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 switch port’s VLAN configuration and ensure the host and router interface are in the same VLAN.
An incomplete ARP entry for the default gateway indicates that the host sent an ARP request but never received a reply. Since the physical layer (cable and switch port) is verified as operational, the most likely cause is a Layer 2 mismatch: the host and the router interface are in different VLANs, preventing the ARP reply from reaching the host. Checking the switch port's VLAN configuration ensures both devices are in the same broadcast domain, which is required for ARP to function.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Check the switch port’s VLAN configuration and ensure the host and router interface are in the same VLAN.
Why this is correct
If the host and gateway are in different VLANs, the ARP request broadcast never reaches the gateway, so the entry stays incomplete. This step directly addresses the most probable Layer 2 fault after excluding physical issues.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Replace the Ethernet cable between the host and the switch.
- ✗
Clear the ARP cache on the host and attempt to ping the gateway again.
- ✗
Check the router’s routing table for a route to the host’s subnet.
Why it's wrong here
The default gateway IP is the router’s own interface address; it does not need a route to respond to an ARP request. ARP resolution is a Layer 2 process for a directly connected network, not a routing decision.
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 switch port’s VLAN configuration and ensure the host and router interface are in the same VLAN.Correct answer▾
Why this is correct
If the host and gateway are in different VLANs, the ARP request broadcast never reaches the gateway, so the entry stays incomplete. This step directly addresses the most probable Layer 2 fault after excluding physical issues.
✗Replace the Ethernet cable between the host and the switch.Wrong answer — click to see why▾
Why this is wrong here
Candidates may equate a physical link symptom with a faulty cable, but the port’s active status indicates a good L1 connection. This action skips necessary logical checks.
✗Clear the ARP cache on the host and attempt to ping the gateway again.Wrong answer — click to see why▾
Why this is wrong here
This is a common ‘quick fix’ mindset, but in a structured troubleshooting process, clearing the cache hides information without solving the root cause.
✗Check the router’s routing table for a route to the host’s subnet.Wrong answer — click to see why▾
Why this is wrong here
Candidates might confuse local ARP failure with reachability issues to a remote subnet, but the gateway is the router itself. Routing is irrelevant until the destination is off-segment.
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?”
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between Layer 2 connectivity (ARP, VLANs) and Layer 3 connectivity (routing), leading candidates to incorrectly focus on routing tables or ARP cache clearing when the real issue is a VLAN mismatch.
Detailed technical explanation
How to think about this question
ARP operates within a single broadcast domain (VLAN). When a host sends an ARP request, it is a Layer 2 broadcast that is confined to the VLAN of the switch port. If the router's interface is in a different VLAN, the ARP request never reaches the router, and the router's ARP reply never reaches the host, resulting in an incomplete ARP entry. This scenario often occurs with router-on-a-stick configurations or when a switch port is accidentally placed in the wrong access VLAN.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A help-desk technician troubleshoots why a newly connected PC cannot reach shared printers on the same floor. The cable is good, the switch port is active, but the PC is in VLAN 20 and the printers are in VLAN 10. The uplink trunk only allows VLAN 10. A trunk being up does not mean every VLAN crosses it.
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this 200-301 question test?
Network Infrastructure and Connectivity — This question tests Network Infrastructure and Connectivity — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Check the switch port’s VLAN configuration and ensure the host and router interface are in the same VLAN. — An incomplete ARP entry for the default gateway indicates that the host sent an ARP request but never received a reply. Since the physical layer (cable and switch port) is verified as operational, the most likely cause is a Layer 2 mismatch: the host and the router interface are in different VLANs, preventing the ARP reply from reaching the host. Checking the switch port's VLAN configuration ensures both devices are in the same broadcast domain, which is required for ARP to function.
What should I do if I get this 200-301 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 25, 2026
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.
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