CCNA Network Infrastructure and Connectivity Practice Question
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?
⚠ Common exam trap
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.
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
✓
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.
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 explicitly shows the port status as 'connected,' meaning the interface is in an operational up/up state, not the 'err-disabled' state. An err-disabled port is automatically shut down due to a security or protocol event and remains down until manually re-enabled or error-disable recovery timer expires. A spanning-tree loop itself does not place a port into err-disabled; loops cause blocking or forwarding transitions managed by STP, and err-disabled would require a feature such as BPDU guard. Therefore, this option does not explain the DHCP failure.
- ✓
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
For a DHCP client in VLAN 100 to obtain an address from a server located in a different VLAN or subnet, the VLAN 100 SVI must include an 'ip helper-address' pointing to the DHCP server. DHCP requests are IP broadcast packets, and routers do not forward broadcasts across interfaces by default; without UDP forwarding configured, the DHCPDISCOVER is never relayed to the server, so the client receives no DHCPOFFER and may fall back to an APIPA address. The correct remedy is to configure 'interface vlan 100' with the 'ip helper-address' command referencing the DHCP server's IP address.
- ✗
The client is in the wrong VLAN; the switch should be configured with VLAN 200.
Why it's wrong here
The show output clearly indicates the access port is assigned to VLAN 100, and there is no evidence in the scenario that the client should belong to VLAN 200. Moving the client to a different VLAN would merely place it in another broadcast domain without solving the underlying issue of DHCP broadcast forwarding, especially if the DHCP server remains in a different subnet. VLAN assignment is an administrative decision based on network design, not a default fix for a DHCP lease failure, so this option is not the cause.
- ✗
There is a duplex mismatch between the client and the switch.
Why it's wrong here
The interface status reports 'a-full' (auto-negotiated full duplex), confirming that both the switch and the client negotiated full duplex, which rules out a duplex mismatch. A true duplex mismatch would occur if one side were forced full duplex while the other remained half duplex, and the output would show 'a-half' or 'half'; it would also generate CRC errors, runts, and late collisions at the physical layer. Even if a mismatch existed, it would not selectively prevent DHCP from working, as DHCP uses only a small amount of bandwidth and can succeed on half-duplex links, so this is not the described problem.
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
For a DHCP client in VLAN 100 to obtain an address from a server located in a different VLAN or subnet, the VLAN 100 SVI must include an 'ip helper-address' pointing to the DHCP server. DHCP requests are IP broadcast packets, and routers do not forward broadcasts across interfaces by default; without UDP forwarding configured, the DHCPDISCOVER is never relayed to the server, so the client receives no DHCPOFFER and may fall back to an APIPA address. The correct remedy is to configure 'interface vlan 100' with the 'ip helper-address' command referencing the DHCP server's IP address.
✗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?”
Visual reference
Go deeper
Related to this question
Learn chapter
IPv4 Addressing and Address Classes
Key term
DHCP
Dynamic Host Configuration Protocol (DHCP) automatically assigns IP addresses and network settings to devices on a network, so they can communicate without manual configuration.
Key term
VLAN
A VLAN (Virtual Local Area Network) is a logical grouping of network devices that behave as if they are on the same physical network segment, regardless of their actual physical location.
About these practice questions
Courseiva writes every 200-301 question from scratch — 1,389 in total, each with an explanation and a wrong-answer breakdown. None are copied from real exams or dumps. Learn why practice questions differ from exam dumps →
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.