CCNA Switching and Network Access Practice Question
Exhibit
Controller status: - 14 APs joined successfully AP-15 status: - Power on: yes - Ethernet link: up - IP address: 10.60.15.44/24 - Default gateway configured: 10.60.14.1 - Controller management IP: 10.60.15.10
A network administrator has several access points. All APs except one have successfully joined the wireless controller. The administrator verifies the failing AP’s IP address, subnet mask, and controller IP address are correctly configured. What is the most likely reason the AP cannot join the controller?
⚠ Common exam trap
Avoid assuming global issues when only one AP is affected; focus on individual AP configuration and connectivity.
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 AP has an incorrect default gateway for its subnet.
The most likely cause is that the AP has an incorrect default gateway. For the AP to reach the controller (which may be on a different subnet), it needs a correct default gateway to route traffic. The other APs joined successfully, eliminating a controller-wide issue. Option B is incorrect because CAPWAP requires an IP address; it does not work without one. Option C is incorrect because CAPWAP uses IP/UDP, not PPP. Option D is unlikely because there is no indication that the controller is at its AP limit; the problem affects only one AP, suggesting an individual misconfiguration.
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 AP has an incorrect default gateway for its subnet.
Why this is correct
If the AP's default gateway is incorrect, the access point cannot route CAPWAP packets off its local subnet to reach a controller on a different IP subnet. CAPWAP discovery and join responses from the controller would never arrive, even though the AP's own IP address and controller discovery mechanism (such as DNS or broadcast) are correctly set. The result is the AP stuck in an unjoined/disabled state, exactly as shown.
- ✗
CAPWAP can be used only if the AP has no IP address.
Why it's wrong here
CAPWAP is an IP protocol that requires both the AP and controller to have valid IP addresses to establish a control and data tunnel. An AP without an IP address could not send or receive the CAPWAP Discovery and Join Request messages. The statement is backwards: the AP must have a valid IP address and IP connectivity, not be without one, making it an incorrect explanation.
When this WOULD be correct
In a different scenario where the question states that an AP is configured without an IP address and is attempting to connect to a controller, this option would be correct. The question could specify that the AP is in a factory default state with no IP configuration.
- ✗
The AP must use PPP instead of Ethernet to reach the controller.
Why it's wrong here
Controller-based APs use CAPWAP, which is carried over UDP/IP and can run over any IP-enabled transport like Ethernet, not a direct PPP link. PPP is a layer 2 encapsulation commonly used on serial links or broadband, and is not required or even typical for a wired CAPWAP join. The exhibit shows an Ethernet path, so a PPP requirement is not the cause of the AP failing to join.
When this WOULD be correct
In a different exam scenario where the question specifies that the AP is configured to use PPP (Point-to-Point Protocol) for its connection, and the controller only supports Ethernet connections, this option would be correct as it would explain the failure to join the controller.
- ✗
The controller can support only 14 APs maximum.
Why it's wrong here
There is no universal IEEE or CAPWAP standard limiting a WLC to 14 APs; the maximum is determined by the controller model, software version, and licensing. The exhibit gives no indication of a capacity threshold being reached, and a capacity exhaustion would typically affect all APs or cause admission failures, not a single AP's gateway misconfiguration. Thus, this option does not explain the observed symptom.
When this WOULD be correct
In a different scenario, if a question stated that a wireless controller can only support a maximum of 14 APs and asked why an additional AP could not join, then this option would be correct as it directly addresses the limitation of the controller's capacity.
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 AP has an incorrect default gateway for its subnet.Correct answer▾
Why this is correct
If the AP's default gateway is incorrect, the access point cannot route CAPWAP packets off its local subnet to reach a controller on a different IP subnet. CAPWAP discovery and join responses from the controller would never arrive, even though the AP's own IP address and controller discovery mechanism (such as DNS or broadcast) are correctly set. The result is the AP stuck in an unjoined/disabled state, exactly as shown.
✗CAPWAP can be used only if the AP has no IP address.Wrong answer — click to see why▾
Why this is wrong here
CAPWAP requires an IP address on the AP to form the control tunnel; it does not function without one.
★ When this WOULD be the correct answer
In a different scenario where the question states that an AP is configured without an IP address and is attempting to connect to a controller, this option would be correct. The question could specify that the AP is in a factory default state with no IP configuration.
Why candidates choose this
Candidates may find this option tempting because they might confuse the requirements for CAPWAP with other protocols that can operate without an IP address, leading to a misunderstanding of the AP's connectivity requirements.
✗The AP must use PPP instead of Ethernet to reach the controller.Wrong answer — click to see why▾
Why this is wrong here
APs communicate with controllers over standard Ethernet using IP; PPP is not required or used in CAPWAP deployments.
★ When this WOULD be the correct answer
In a different exam scenario where the question specifies that the AP is configured to use PPP (Point-to-Point Protocol) for its connection, and the controller only supports Ethernet connections, this option would be correct as it would explain the failure to join the controller.
Why candidates choose this
Candidates may find this option tempting due to a misunderstanding of CAPWAP protocols and their requirements, leading them to incorrectly associate IP address assignment with connectivity issues.
✗The controller can support only 14 APs maximum.Wrong answer — click to see why▾
Why this is wrong here
While controllers have AP license limits, there is no evidence that the limit is exactly 14 or that it has been exceeded. The issue is isolated to one AP, pointing to a per-device problem.
★ When this WOULD be the correct answer
In a different scenario, if a question stated that a wireless controller can only support a maximum of 14 APs and asked why an additional AP could not join, then this option would be correct as it directly addresses the limitation of the controller's capacity.
Why candidates choose this
Candidates may find this option tempting because they might recall limitations on device connections in networking, leading them to assume that capacity issues could affect AP connectivity without considering other factors.
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
Quick reference
IPv4 Address Class Summary
| Class | First Octet Range | Default Mask | Networks | Hosts per Network |
|---|---|---|---|---|
| A | 1–126 | /8 (255.0.0.0) | 126 | 16,777,214 |
| B | 128–191 | /16 (255.255.0.0) | 16,384 | 65,534 |
| C | 192–223 | /24 (255.255.255.0) | 2,097,152 | 254 |
| D | 224–239 | N/A | Multicast groups | — |
| E | 240–255 | N/A | Reserved / experimental | — |
127.x.x.x is reserved for loopback. Modern networks use CIDR (classless) rather than classful addressing.
Go deeper
Related to this question
Learn chapter
Interpreting Packet Capture Output for Layer 2/3 Troubleshooting
Key term
Subnet
A subnet is a logical subdivision of an IP network, created by partitioning a larger network address space using subnet masks.
Key term
IP address
An IP address is a unique numerical label assigned to each device connected to a computer network that uses the Internet Protocol for communication.
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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.