Cisco CCNA WLAN Architectures and Concepts Questions and Answers

Question 1

A network administrator is designing a wireless network for a large corporate campus with hundreds of access points. The requirements include centralized management, seamless client roaming, and consistent policy enforcement. Which WLAN architecture is BEST suited for this scenario?

Accepted Answer

Controller-based architecture

Answer

A controller-based architecture, also known as a Split-MAC architecture, is the ideal solution for large-scale enterprise deployments. It uses a central Wireless LAN Controller (WLC) to manage all lightweight access points (LAPs), providing centralized configuration, policy enforcement, firmware updates, and facilitating seamless roaming. [2, 5, 8] Autonomous APs require individual configuration, which is not scalable. [1, 2] Ad-hoc mode is for peer-to-peer connections without an AP. Cloud-based management is a valid option, but managing each AP individually negates the benefits of centralization required for this scale.

Question 2

In a controller-based WLAN architecture using CAPWAP, what is the primary function of the 'Split-MAC' concept?

Accepted Answer

It divides the 802.11 MAC functions between the Lightweight Access Point (LAP) and the Wireless LAN Controller (WLC).

Answer

The Split-MAC architecture is a fundamental concept in controller-based WLANs. It divides the 802.11 MAC operations, assigning real-time functions (like beaconing and probe responses) to the Lightweight Access Point, while the Wireless LAN Controller handles less time-sensitive management functions (like authentication and association). [3, 7, 17] This allows for centralized control while keeping time-critical operations close to the client.

Question 3

A company needs to deploy a wireless access point in a small, remote branch office with an unreliable WAN link to the central headquarters where the WLC is located. The goal is to allow wireless clients to continue accessing local resources even if the WAN link fails. Which AP mode should the administrator configure?

Accepted Answer

FlexConnect Mode

Answer

FlexConnect mode is specifically designed for remote/branch office deployments. In this mode, if the CAPWAP tunnel to the WLC is down, the AP can switch traffic locally between the wireless clients and the wired LAN, allowing access to local resources. [4, 20, 23] Local mode, the default, requires the CAPWAP tunnel to be active as it tunnels all traffic back to the WLC. [20, 25] Monitor and Sniffer modes are used for network monitoring and troubleshooting, not for serving clients. [4]

Question 4

Which of the following correctly describes the CAPWAP tunnels established between a Lightweight Access Point (LAP) and a Wireless LAN Controller (WLC)?

Accepted Answer

Two separate UDP tunnels are used: a control tunnel on port 5246 and a data tunnel on port 5247.

Answer

CAPWAP establishes two distinct UDP tunnels between the LAP and WLC. The control tunnel operates on UDP port 5246 and is used for management and control traffic; it is secured by default with DTLS encryption. The data tunnel operates on UDP port 5247 and is used to encapsulate and forward client data; it is unencrypted by default. [3, 7, 14, 26]

Question 5

A wireless client roams from an AP associated with WLC1 to an AP associated with WLC2. Both WLCs are in the same mobility group, but the client is assigned to a different VLAN/subnet after roaming. To maintain the client's session and IP address, what type of roaming occurs?

Accepted Answer

Layer 3 Inter-controller Roaming

Answer

When a wireless client roams between APs connected to different WLCs and moves to a new VLAN/subnet, it is called a Layer 3 Inter-controller roam. To ensure seamless connectivity, the original WLC becomes the 'anchor' controller, and a mobility tunnel (often a CAPWAP or EoIP tunnel) is built between the anchor and the new 'foreign' controller. This allows the client to keep its original IP address by tunneling its traffic back to the original subnet. [13, 16, 21]

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Cisco CCNA WLAN Architectures and Concepts Questions and Answers