The answer is a missing ip helper-address on the VLAN 100 SVI, because the 169.254.10.15 address is an APIPA address cause that directly indicates DHCP failure. When a Windows client cannot reach a DHCP server, it self-assigns an APIPA address in the 169.254.x.x range, and since the switch port is up/up in VLAN 100, the client’s DHCP broadcast is never forwarded beyond that VLAN. On the CCNA 200-301 v2 exam, this scenario tests your understanding of DHCP relay and Layer 3 interface configuration—a common trap is assuming the switch port itself is faulty, but the real issue is that the SVI lacks the ip helper-address command to forward broadcasts to the DHCP server. Remember, APIPA always points to a DHCP communication breakdown, not a physical link problem. Memory tip: “No helper, no DHCP—APIPA is the last resort.”
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.
Exhibit
C:\) ipconfig
Ethernet adapter Local Area Connection:
Connection-specific DNS Suffix . :
IPv4 Address. . . . . . . . . . . : 169.254.10.15
Subnet Mask . . . . . . . . . . . : 255.255.0.0
Default Gateway . . . . . . . . . :
Switch# show interfaces gigabitethernet 0/1 status
Port Name Status Vlan Duplex Speed Type
Gi0/1 connected 100 a-full a-100 10/100/1000BaseTX
Switch# show running-config interface gigabitethernet 0/1
Building configuration...
Current configuration : 100 bytes
!
interface GigabitEthernet0/1
description Client Access Port
switchport mode access
switchport access vlan 100
spanning-tree portfast
end
A network administrator is troubleshooting a Windows 10 client that cannot reach the internet. The client is connected to a Cisco switch port configured as an access port in VLAN 100. The administrator runs ipconfig on the client and sees an IP address of 169.254.10.15 with a subnet mask of 255.255.0.0. The switch port shows status up/up. What is the most likely cause of the issue?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The switch is not configured with an ip helper-address on the VLAN 100 SVI to forward DHCP broadcasts to the DHCP server.
The 169.254.x.x address is an Automatic Private IP Addressing (APIPA) address, assigned by Windows when DHCP fails. Since the client is in VLAN 100 and the switch port is up/up, the most likely cause is that the VLAN 100 SVI lacks an ip helper-address command, so DHCP broadcast requests from the client are not forwarded to the DHCP server, leaving the client without a valid IP address.
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.
✗
The switch port is in err-disabled state due to a spanning-tree loop.
Why it's wrong here
The output shows the port is 'connected', not err-disabled, so this is not the issue.
✓
The switch is not configured with an ip helper-address on the VLAN 100 SVI to forward DHCP broadcasts to the DHCP server.
Why this is correct
Without an ip helper-address, DHCP broadcasts from the client in VLAN 100 are not forwarded to the DHCP server, which is likely in a different VLAN.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The client is in the wrong VLAN; the switch should be configured with VLAN 200.
Why it's wrong here
The switchport is configured for VLAN 100, and there is no evidence that the client should be in a different VLAN.
✗
There is a duplex mismatch between the client and the switch.
Why it's wrong here
The switch reports 'a-full' (auto-negotiated full duplex), indicating no duplex mismatch.
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.
✓The switch is not configured with an ip helper-address on the VLAN 100 SVI to forward DHCP broadcasts to the DHCP server.Correct answer▾
Why this is correct
Without an ip helper-address, DHCP broadcasts from the client in VLAN 100 are not forwarded to the DHCP server, which is likely in a different VLAN.
✗The switch port is in err-disabled state due to a spanning-tree loop.Wrong answer — click to see why▾
Why this is wrong here
The port status is 'connected', not err-disabled.
✗The client is in the wrong VLAN; the switch should be configured with VLAN 200.Wrong answer — click to see why▾
Why this is wrong here
No information suggests the client should be in VLAN 200; the configuration matches the intended VLAN.
✗There is a duplex mismatch between the client and the switch.Wrong answer — click to see why▾
Why this is wrong here
Duplex mismatch would typically cause errors or speed/duplex issues, but the switch shows a-full, so this is not the problem.
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 misconception that an APIPA address indicates a physical or VLAN issue, when in fact it specifically points to DHCP failure, and the most common cause in a routed environment is the absence of ip helper-address on the SVI.
Trap categories for this question
Command / output trap
The output shows the port is 'connected', not err-disabled, so this is not the issue.
Detailed technical explanation
How to think about this question
DHCP uses UDP broadcasts (source port 68, destination port 67) that are typically not forwarded across subnets by routers. The ip helper-address command on a Cisco switch's SVI (interface vlan 100) converts the broadcast into a unicast directed to the DHCP server, using the relay agent's IP address as the giaddr field. Without this command, the DHCPDISCOVER broadcast remains within VLAN 100 and never reaches the DHCP server, forcing the client to fall back to APIPA (RFC 3927).
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 200-301 question in full detail.
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: The switch is not configured with an ip helper-address on the VLAN 100 SVI to forward DHCP broadcasts to the DHCP server. — The 169.254.x.x address is an Automatic Private IP Addressing (APIPA) address, assigned by Windows when DHCP fails. Since the client is in VLAN 100 and the switch port is up/up, the most likely cause is that the VLAN 100 SVI lacks an ip helper-address command, so DHCP broadcast requests from the client are not forwarded to the DHCP server, leaving the client without a valid IP address.
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.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
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These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A network administrator is troubleshooting a user's wired workstation that cannot access the internet. The user reports that the workstation was working earlier today. The administrator runs 'ipconfig /all' on the workstation and sees an IP address of 169.254.10.55. What is the most likely cause of this issue?
medium
A.The workstation has a duplicate IP address conflict with another device.
✓ B.The workstation is unable to communicate with a DHCP server due to a faulty network cable.
C.The workstation's DNS server settings are misconfigured.
D.The workstation is connected to the wrong VLAN, causing it to receive an incorrect IP address.
Why B: The IP address 169.254.10.55 falls within the Automatic Private IP Addressing (APIPA) range (169.254.0.0/16, RFC 3927). This address is assigned by the operating system when a DHCP client fails to receive a response from a DHCP server. A faulty network cable would prevent the workstation from communicating with the DHCP server, causing the client to self-assign an APIPA address after the DHCP discovery process times out.
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Question Discussion
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