In an anchored WLAN deployment, client traffic is encapsulated within CAPWAP mobility tunnels between the foreign WLC (where the AP joins) and the anchor WLC (in the DMZ or designated network segment). This tunneling adds encapsulation overhead — CAPWAP/mobility tunnel headers consume a portion of the available MTU on the transport path. When video streaming clients generate large TCP segments, these segments may exceed the effective MTU of the mobility tunnel path, causing IP fragmentation at the WLC or along the path to the anchor. Fragmentation significantly degrades throughput and increases CPU overhead for high-volume video traffic. The correct solution is TCP MSS Clamping — reducing the Maximum Segment Size value advertised in TCP SYN packets so that TCP endpoints negotiate a segment size remaining below the fragmentation threshold. The Cisco 9800 WLC supports TCP MSS adjustment, which intercepts TCP handshake packets and rewrites the MSS option to a value accounting for CAPWAP tunnel overhead. Setting matching MTUs (Option A) does not prevent fragmentation if the effective tunnel MTU is lower than the client segment size. Increasing the MTU (Option B) is often constrained by physical infrastructure. Setting the DF bit (Option D) would cause packets to be dropped rather than fragmented. Reference: WLSD Study Guide — Anchored WLAN Design, CAPWAP Mobility Tunnel MTU, TCP MSS Clamping.

Designing for 50-100 clients per cell with 5 Mbps minimum throughput and no 802.11b clients requires two critical optimizations. First, setting minimum mandatory data rates to 12-18 Mbps (Option A) removes legacy lower data rates from the AP ' s supported rate set. When 1, 2, 5.5, and 11 Mbps rates are disabled and 12 Mbps becomes the minimum mandatory rate, legacy 802.11b clients are excluded from the cell, airtime efficiency improves dramatically, and clients connecting at higher rates use less channel time per frame, increasing effective capacity. Second, Flexible Radio Assignment (FRA) for 2.4 GHz reduction (Option D) is critical in high-density environments. FRA allows the WLC to dynamically reassign some 2.4 GHz radios to 5 GHz operation or monitor mode, reducing 2.4 GHz cell size and interference while increasing 5 GHz capacity in the high-density area. Option C directly contradicts the no-802.11b requirement. Option B (6 SSIDs per AP) is a management consideration but does not directly address throughput. Option E (80-160 MHz channels) would consume available spectrum, reducing the number of usable non-overlapping channels and worsening co-channel interference at high density. Reference: WLSD Study Guide — High-Density WLAN Design, Minimum Data Rate Configuration, Flexible Radio Assignment (FRA).

To support high availability with client SSO (Stateful Switchover) and no interruption to live services during failover, the design must incorporate two requirements. First, redundant WLCs (Option A) are essential — without a physical standby controller, there is no entity to take over when the primary WLC fails. In an SSO configuration, one WLC is active and one is standby, and the standby must be ready to assume the active role instantaneously. Second, the high availability pair requires one of the WLCs to have a valid AP count license (Option B). In a Cisco WLC SSO pair, the standby controller ' s AP count license applies when it becomes active — without a valid license on at least one WLC in the pair, APs cannot join after failover. A 10-second RTT maximum (Option C) is a latency requirement for the redundancy link but is not a primary design requirement that addresses the overall high availability architecture. A back-to-back direct connection (Option D) is one way to connect the redundancy ports but is not mandatory if a low-latency switch connection is used. Code version 7.5 or newer (Option E) is a requirement for specific legacy SSO platforms but not a general design principle. Reference: WLSD Study Guide — WLC SSO High Availability Design, AP License Requirements, Redundant Controller Architecture.