mediumMultiple Choice
350-401 CAPWAP Discovery Practice Question
A network engineer is deploying a new wireless LAN controller (WLC) in a campus network. The WLC must manage 200 access points across three buildings. The engineer configures the WLC with a management IP address and enables CAPWAP. However, the access points fail to join the WLC. The APs are in the same VLAN as the WLC and can ping the WLC's management IP. What is the most likely cause of the APs not joining?
⚠ Common exam trap
The trap is that candidates may assume that because APs can ping the WLC, they should be able to join automatically. In reality, APs need to discover the WLC, which commonly relies on DHCP option 43. Without it, APs cannot initiate the CAPWAP join process even with layer 3 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 APs are not configured with DHCP option 43 to point to the WLC.
The APs are in the same VLAN and can ping the WLC, but they still fail to join. Since the APs use DHCP by default, they rely on DHCP option 43 to obtain the WLC's IP address for CAPWAP discovery. Without this option, the APs do not know which WLC to join, even though they have IP connectivity. Option A is incorrect because the management interface is the default CAPWAP source; a separate source interface is not required for APs in the same VLAN.
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 WLC does not have a CAPWAP source interface configured.
Why it's wrong here
This is incorrect. On Cisco WLCs, the management interface serves as the default CAPWAP source. Not configuring an explicit CAPWAP source interface does not prevent APs from joining when they are in the same VLAN and reachable.
- ✓
The APs are not configured with DHCP option 43 to point to the WLC.
Why this is correct
This is correct. APs typically use DHCP to obtain an IP address and look for DHCP option 43 to discover the WLC. Without option 43, they cannot find the WLC even if they have IP connectivity.
- ✗
The APs are running an incompatible IOS version that does not support CAPWAP.
Why it's wrong here
CAPWAP is supported by virtually all Cisco lightweight APs and IOS/IOS-XE releases, so an incompatible IOS version is an unlikely root cause; even legacy LWAPP-based APs can join modern WLCs because the WLC supports both protocols. If the AP were truly running an image without CAPWAP support, it would either fail to boot in lightweight mode or remain in a loop, not simply fail to find the WLC. The more probable and common issue is a missing DHCP option 43, which directly affects AP discovery rather than protocol capability.
- ✗
The APs must be assigned a static IP address to join the WLC.
Why it's wrong here
Requiring a static IP address is false because Cisco APs can dynamically obtain an IP address via DHCP and still successfully join a WLC; static addressing is purely an administrative choice, not a technical prerequisite. The CAPWAP join process only needs the AP to have valid IP connectivity to the WLC and a discovery method (such as DHCP option 43, DNS, or local broadcast) to locate the controller. In fact, most production deployments use DHCP for scale and ease of management, so the absence of a static IP would not prevent an AP from joining.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 350-401 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 350-401 exam.