What provides centralized control of authentication and roaming in an (CCNA 200-301)

Correct answer: B. a wireless LAN controller.
A wireless LAN controller (WLC) is a centralized device that provides control and management functions for wireless access points (APs) in an enterprise network. Some of the key responsibilities of a WLC include:

Authentication and Authorization: The WLC handles the authentication of wireless clients, ensuring that only authorized users can access the network. It integrates with various authentication mechanisms, such as RADIUS, to provide centralized user authentication.
Roaming: The WLC facilitates seamless roaming for wireless clients as they move between different access points within the enterprise network. It manages the handoff process and ensures that client sessions are maintained during the transition.
Wireless Policy Enforcement: The WLC enforces wireless policies, such as access control, quality of service (QoS), and security settings, across the entire wireless network.
Centralized Configuration and Management: The WLC allows for the centralized configuration and management of wireless APs, simplifying the deployment and maintenance of the wireless infrastructure.

The other options are not directly responsible for centralized control of authentication and roaming in an enterprise network:
A. A lightweight access point is a wireless AP that relies on a WLC for most of its functionality and control.
C. A firewall is primarily responsible for network security and access control, not for wireless network management.
D. A LAN switch is responsible for switching and forwarding Ethernet frames, but does not provide centralized wireless network control.

Therefore, the wireless LAN controller (WLC) is the correct answer as it provides the centralized control of authentication and roaming in an enterprise wireless network.