In the WAC+FITAP networking mode, which option field of the DHCP protocol can the AP use to discover the WAC device?

Question

Options

• Aoption 12
• Boption 82
• Coption 148
• Doption 43

• A
  14% (7)
• B
  4% (2)
• C
  6% (3)
• D
  76% (39)

Explanation

DHCP Option 43 (Vendor-Specific Information) is correct because it allows the DHCP server to embed vendor-specific data - in this case, the IP address of the WAC (Wireless Access Controller) - directly in the DHCP offer sent to the AP during the boot/discovery process. The Fit AP receives this option and uses the embedded WAC address to initiate its CAPWAP tunnel, completing the WAC+FITAP association without manual configuration.

Why the distractors are wrong:

• Option 12 carries the client's hostname - it identifies devices, not controllers.
• Option 82 is the relay agent information option, added by DHCP relay agents to convey circuit/port info to the server; it plays no role in WAC discovery.
• Option 148 has no standard role in WAC+FITAP discovery and is a plausible-sounding distractor; some Cisco LWAPP implementations used non-standard options, but Option 43 is the vendor-neutral, standards-based mechanism adopted for this purpose.

Memory tip: Option 43 = "43 = vendor" - it's the vendor-specific option, so it's the natural choice for a vendor (like Huawei) to stuff its own controller address into. If the AP needs to find its gear, it looks in the vendor box.

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