350-401 Question 172
Select 4A network engineer is deploying a new Cisco wireless network with multiple access points (APs) and wireless LAN controllers (WLCs). During the AP discovery and join process, which of the following methods can the AP use to discover a WLC?
- A
Broadcasting a CAPWAP discovery request on the local subnet
- B
Using DNS to resolve 'cisco-capwap-controller.localdomain'
- C
Querying a DHCP server for Option 43
- D
Manually configuring the WLC IP address on the AP
- E
Using Layer 2 MAC address table lookup for WLC discovery
Show answer and explanation
Correct answers: A, B, C, D
Explanation
During the discovery and join process, Cisco access points use several methods to locate a wireless LAN controller. These include broadcasting CAPWAP discovery requests on the local subnet, using DNS to resolve a predefined hostname, querying DHCP for Option 43, or manually configuring the WLC IP address. Each of these methods enables the AP to establish communication with a WLC. However, Layer 2 MAC address table lookups are not part of the WLC discovery process, as it primarily relies on Layer 3 mechanisms.
- A. Correct.
Correct. The AP broadcasts a CAPWAP discovery request on the local subnet to find a WLC. This is a common first step in the discovery process.
- B. Correct.
Correct. The AP can use DNS to resolve a predefined hostname ('cisco-capwap-controller.localdomain') to discover the WLC's IP address.
- C. Correct.
Correct. The AP can query a DHCP server for Option 43, which provides the IP address of the WLC in the response.
- D. Correct.
Correct. Manually configuring the WLC IP address on the AP is a valid method for discovery, although it may not be practical in large-scale deployments.
- E. Incorrect.
Incorrect. APs do not use Layer 2 MAC address table lookups for WLC discovery. The discovery process relies on Layer 3 methods such as CAPWAP, DNS, and DHCP.