An RTS frame is an 802.11 control frame used in the Request to Send/Clear to Send exchange.
Cisco identifies RTS as a Request to Send frame and explains that 802.11 control frames assist in delivering data frames between stations. Cisco further states that the RTS/CTS function is optional, helps reduce collisions when hidden stations are associated to the same access point, and that a station sends an RTS frame as the first phase before transmitting a data frame.
Therefore, option B is correct because the RTS frame requests access to the wireless medium before data transmission. If the receiving station or AP replies with CTS, nearby stations defer transmission based on the duration information, reducing collision probability. This is especially relevant in hidden-node environments where two clients can hear the AP but cannot hear each other. Option A refers to RF spectral-mask compliance, which is a physical-layer regulatory concept. Option C confuses NAV behavior with roaming; RTS/CTS may influence virtual carrier sensing, not client roaming updates. Option D is unrelated because frame compression is not an RTS function.

A line-of-sight (LOS) RF connection requires a clear, unobstructed path between the transmitter and receiver. This ensures that the transmitted signal reaches the receiving device without attenuation, reflection, or diffraction caused by physical obstacles such as walls, furniture, or other structures. LOS conditions are critical for high-frequency RF links, particularly in the 5 GHz band, where signals cannot easily penetrate objects.

The requirement is guest client isolation, not merely guest authentication or internet breakout. On a Catalyst 9800 WLC, peer-to-peer blocking is the correct control because it prevents wireless clients associated to the same WLAN from communicating directly with one another. Cisco defines peer-to- peer blocking as a WLAN security feature applied to individual WLANs, where each client inherits the WLAN's P2P blocking behavior, and traffic can be bridged locally, dropped, or forwarded upstream. For this scenario, the appropriate action is the drop behavior, because guest-to-guest file sharing must be prohibited while upstream internet access remains available.
The dedicated guest VLAN, VLAN 30, provides traffic segmentation from production networks and creates a clean policy boundary for VisitorAccess. Cisco's Catalyst 9800 configuration model maps WLANs to policy profiles, and the policy profile defines client network and switching policy, including VLAN association. Options B, C, and D do not solve client isolation: local authentication validates users, FlexConnect/local switching changes traffic forwarding behavior, and multicast/RADIUS does not block unicast guest-to-guest traffic.

The correct answer is fast BSS transition protocol, which is IEEE 802.11r Fast Transition. Cisco describes 802.11r BSS Fast Transition as the mechanism used to provide seamless roaming for wireless clients by reducing the time required to roam between access points. It achieves this by allowing keying material to be prepared or cached so that the client does not perform a full authentication exchange every time it moves to another AP within the same mobility domain.
This is specifically relevant to Layer 2 roaming because the client remains in the same Layer 2 network while reassociating to a different BSS. Fast Transition reduces roam latency, which is critical for voice, video, collaboration, barcode scanners, and other real-time applications. Cisco also classifies fast secure roaming as the method used to accelerate client roaming when Layer 2 security is configured on the WLAN. Increased beacon intervals do not provide handoff acceleration. Optimized roaming helps with sticky-client behavior but is not the secure handoff protocol. Deferred probe response is an RF/client steering behavior, not an 802.11 Layer 2 roaming key-transition method.

FlexConnect mode allows access points at remote sites to switch traffic locally while maintaining centralized management through the controller. During WAN outages, APs can continue authenticating clients locally and provide uninterrupted wireless access. Monitor and Sniffer modes are for analysis purposes, not client servicing or survivability operations.