In a WLAN network, when there is an IPv4 Layer 3 networking between the AC and AP, the user needs to configure the Option43 field. Which of the following functions does it mainly implement?

Question

Options

• ASet DNS server address options
• BSet AC management address options
• CSet gateway address options
• DSet subnet mask options

• A
  6% (3)
• B
  78% (40)
• C
  4% (2)
• D
  12% (6)

Explanation

Option 43 (Vendor-Specific Information) is used in DHCP to carry vendor-specific data, and in WLAN deployments it is the standard mechanism for a DHCP server to tell an AP the IP address of its Wireless LAN Controller (AC/Access Controller) - enabling the AP to discover and register with the AC automatically during boot.

Why the distractors are wrong:

• A (DNS server) - DNS server addresses are conveyed in DHCP Option 6, not Option 43.
• C (Gateway address) - The default gateway is carried in DHCP Option 3.
• D (Subnet mask) - The subnet mask is part of the core DHCP offer (Option 1), not Option 43.

Memory tip: Think of Option 43 as the "find your boss" option - when an AP comes online with no pre-configured controller address, DHCP Option 43 points it to the AC (its "boss") so it can check in and be managed. All the other options (DNS, gateway, mask) have their own dedicated, well-known option numbers.

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