Which port is required for APs to join a WLC using directed broadcasts?

350-401 By islever Editorial Last updated

Short answer

A UDP 5246

Question

Which port is required to allow APs to join a WLC when directed broadcasts are used on a Cisco IOS switch?
  1. UDP 5246 Correct Answer
  2. TCP 5246
  3. TCP 5247
  4. UDP 5247

Key Takeaways

The exam tests your knowledge of CAPWAP port numbers and transport protocols; the common trap is confusing UDP vs. TCP or mixing up 5246 (control) with 5247 (data).

CAPWAP discovery between Cisco APs and a WLC uses UDP port 5246 for control messages and UDP port 5247 for data messages. Community consensus confirms UDP 5246 is the correct answer for the discovery/join process over directed broadcasts.

Common mistake: Many candidates choose TCP 5246 or UDP 5247, forgetting that CAPWAP discovery and control traffic is strictly UDP 5246, while UDP 5247 is reserved for the data tunnel.

Expert Analysis

Why the Answer Is Correct

CAPWAP (Control and Provisioning of Wireless Access Points) uses UDP port 5246 for all control-plane messages, including the initial Discovery Request and Discovery Response exchanged between an AP and a WLC. When an AP uses directed broadcasts on a Cisco IOS switch, it sends a CAPWAP Discovery Request via UDP 5246 to the broadcast address of the local subnet. The WLC replies on the same UDP port, completing the discovery phase before the data tunnel on UDP 5247 is established. Community comments consistently cite the Official Certification Guide (OCG, p. 523) confirming this behavior.

Why the Other Options Are Wrong

Option B (TCP 5246) is incorrect because CAPWAP never uses TCP for discovery or control messaging; it is entirely UDP-based. Option C (TCP 5247) is wrong for the same reason—TCP is not part of the CAPWAP protocol suite. Option D (UDP 5247) is the CAPWAP data port used for encapsulated wireless traffic after the AP has already joined the WLC, not for the initial discovery and join process itself.

Community Comment Notes

Multiple high-voted comments reinforce that UDP 5246 handles control messages and UDP 5247 handles data messages, directly aligning with Cisco documentation. One comment helpfully breaks down the full discovery sequence: unicast or broadcast CAPWAP Discovery Request on UDP 5246, followed by a Discovery Response from the WLC. Another comment references the OCG page 523, providing an authoritative source that students should review for the complete AP-WLC join process.

Exam Strategy

Memorize that CAPWAP control is always UDP 5246 and CAPWAP data is always UDP 5247. When the question mentions 'discovery,' 'join,' or 'directed broadcast,' immediately select UDP 5246.

Community Votes

A
100%

100% of anonymous learners picked answer A. Votes are pick records left by other test-takers — they are not the verified answer.

Discussion 5 contributions

Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.

From public community threads 5

  1. Shri_Fcb10 👍 5 Answered A
    When allowing APs to join a Wireless LAN Controller (WLC) using directed broadcasts on a Cisco IOS switch, the relevant ports are UDP ports 5246 and 5247. These ports are used for CAPWAP (Control and Provisioning of Wireless Access Points) communication between the APs and the WLC. Specifically: - UDP port 5246 is used for CAPWAP control messages. - UDP port 5247 is used for CAPWAP data messages. Given the options provided, the correct answer for the control channel required for APs to join a WLC is:
  2. aatechler 👍 2 Answered A
    Discovering Wireless LAN Controller The AP sends a unicast CAPWAP Discovery Request to a controller’s IP address over UDP port 5246 or a broadcast to the local subnet to find a WLC. The available WLC sends back a CAPWAP Discovery Response. The discovery process involves the following:
  3. aatechler 👍 2 Answered A
    UDP 5246 for control messages UDP 5247 for data messages
  4. yasmiine 👍 1 Answered A
    Answer A. Lors d'une tentative de découverte d'un WLC, un point d'accès peut envoyer une requête de découverte CAPWAP monodiffusion à l'adresse IP d'un contrôleur via le port UDP 5246 ou peut envoyer une diffusion via le sous-réseau local.
  5. shefo1 👍 1 Answered A
    A is right | form OCG p,523 To discover a WLC, an AP sends a unicast CAPWAP Discovery Request to a controller’s IP address over UDP port 5246 or a broadcast to the local subnet

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