Cisco Designing Cisco Wireless Networks 300-110 WLSD Exam Questions

Answer : B

To optimize roaming in a wireless network with multiple controllers, it is essential to use the same WLAN name (SSID) across all controllers. When SSIDs differ between controllers, clients perceive them as different networks and must perform a full re-association and re-authentication when roaming between APs managed by different controllers. This causes a roaming disruption equivalent to connecting to an entirely new network. By using identical SSID names on both controllers, clients can seamlessly roam between APs on different controllers within the same mobility group --- the controllers exchange client state information via the mobility tunnel, enabling seamless handoff. In the scenario described, 'Copr-NET390595865WLC-1' and 'Copr-NET6837l638WLC-2' are different SSIDs, meaning clients cannot roam transparently between them. Making both controllers broadcast the same SSID name (and using a mobility group to connect the controllers) resolves this. Reference: WLSD Study Guide --- SSID Consistency Across Controllers, Inter-Controller Roaming, Mobility Group Configuration.

Answer : A

Cisco's Embedded Wireless Controller (EWC) architecture is the ideal solution for small deployments with strict budget constraints where only the access points can be replaced. EWC is a controller function that runs directly within the Cisco Catalyst 9100 Series access point itself --- eliminating the need for a dedicated physical or virtual WLC appliance. The APs serve dual roles as both the wireless radio infrastructure and the controller platform. The unified model (Option B) requires a dedicated hardware WLC such as the 9800 series, exceeding the customer's budget. Fabric (Option C) requires Cisco DNA Center and SD-Access infrastructure, making it cost-prohibitive for a small deployment. Cloud (Option D) requires ongoing subscription fees that may not fit a fixed one-time budget. EWC provides enterprise-grade features including centralized SSID management, RRM, and client mobility within the AP cluster --- all without additional controller hardware investment. This makes it the canonical solution for SMB migrations from autonomous deployments. Reference: WLSD Study Guide --- Controller Deployment Models, Embedded Wireless Controller Architecture, SMB and Branch Wireless Design.

Answer : C, D

In an N+1 redundancy deployment, an AP's ability to return to its designated primary WLC after that controller recovers depends on two distinct configuration requirements working in concert. First, the AP Fallback feature (Option C) must be enabled on the WLC. AP Fallback instructs APs to monitor the availability of their configured primary controller and automatically reconnect to it when it becomes available again, rather than remaining permanently joined to the N+1 backup controller. Without AP Fallback enabled, APs stay connected to whichever controller they most recently joined. Second, the APs must have their primary WLC information correctly configured (Option D). If an AP does not have the primary controller's name, IP address, or FQDN correctly set, it cannot identify when its designated primary has recovered and therefore cannot initiate a return fallback. DHCP Option 43 (Option A) is used for initial AP discovery only. Secondary WLC configuration (Option B) addresses failover direction but not the return path. AP failover priority (Option E) controls which APs are moved first during a failover event, not whether fallback occurs. Reference: WLSD Study Guide --- N+1 Redundancy Design, AP Fallback Configuration, Controller Primary, Secondary and Tertiary Assignment.

Answer : D

When eping (EoIP ping) fails between two Cisco Wireless LAN Controllers, it indicates that the data path of the mobility tunnel is blocked. In Cisco AireOS wireless networks, the mobility data path uses IP Protocol 97 (EtherIP --- Ethernet-over-IP encapsulation) for tunneling client traffic between the anchor and foreign controllers. This is distinct from the control path, which uses UDP port 16666. When the mobility data path (IP Protocol 97) is blocked by a firewall or ACL between the two controllers' networks, eping will fail because eping specifically tests the EoIP data encapsulation path. After a power cut, when clients disconnect and attempt to roam between APs on different controllers, the mobility tunnel must be operational for session continuity. If IP Protocol 97 is blocked, the mobility data plane cannot function, causing client disconnections during inter-controller roaming events. The other IP protocols listed (67, 77, 87) are not used for Cisco WLC mobility tunneling. Reference: WLSD Study Guide --- Mobility Tunnel Data Path, IP Protocol 97 (EtherIP), eping Command and Troubleshooting.

Answer : A

The hidden node problem is a classic RF design flaw that emerges when APs transmit at excessive power levels relative to the attenuation characteristics of the environment. In a brick-walled building, AP signals penetrate walls with significant attenuation. When an AP transmits at maximum power, its signal propagates far beyond the intended cell boundary and reaches client devices that may be physically near other APs but unable to detect the original transmitting AP due to wall attenuation between them. These clients can hear the distant AP's signal but cannot hear each other --- making them hidden from one another. This leads to simultaneous transmissions, frame collisions at the AP receiver, and dramatic throughput degradation. The 802.11 CSMA/CA mechanism depends on all stations being able to sense the medium before transmitting; hidden nodes defeat this mechanism entirely. The WLSD curriculum consistently identifies excessive AP transmit power in high-attenuation environments as a primary cause of hidden node conditions. The solution is to reduce AP transmit power so that cell sizes remain appropriate for the physical environment. Reference: WLSD Study Guide --- RF Design Fundamentals, Hidden Node Problem, Transmit Power and Cell Size Optimization.

Answer : A, D

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, clients that cannot achieve at least 12 Mbps are rejected from the cell, maintaining throughput standards. Without this, a single 802.11b client operating at 1 Mbps can consume an inordinate share of airtime and reduce throughput for all other clients below the required minimum. 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. Option C contradicts the no-802.11b requirement. Option B is a management concern, not a throughput solution. Option E (80-160 MHz channels) would consume available spectrum and reduce non-overlapping channels, worsening co-channel interference at high density. Reference: WLSD Study Guide --- High-Density WLAN Design, Minimum Data Rate Configuration, Flexible Radio Assignment (FRA).

Answer : A

This question requires a straightforward PoE power budget calculation. The IEEE 802.3at standard (PoE+) delivers a maximum of 30W at the Power Sourcing Equipment (PSE/switch port). Cisco 9100 Series access points such as the C9120, C9130, and C9136 are designed to operate with full functionality using PoE+ at 30W per AP. The total PoE power requirement for 12 APs is calculated as: 12 APs 30W per AP = 360W. This figure represents the total power draw that the Cisco 3800 Series PoE+ switch must be capable of supplying across the connected AP ports simultaneously. The Cisco Catalyst 3800 Series switches offer a total PoE power budget that must be validated against this 360W requirement during the design phase. Note that some Cisco 9100 APs support higher power modes through IEEE 802.3bt (PoE++), which can provide up to 90W --- but the question specifies PoE+ (802.3at) for the switch infrastructure, making 30W 12 = 360W the correct answer. Option D (720W) would correspond to 24 APs at 30W each. Option B (1080W) would represent 36 APs. Option C (184.8W) corresponds to a non-standard per-AP power value. Reference: WLSD Study Guide --- PoE Power Budget Planning, Cisco 9100 Series AP Power Requirements, Wired Infrastructure Design for Wireless Deployments.