300-425 Designing Cisco Enterprise Wireless Networks (ENWLSD) Questions and Answers

 Cisco Hyperlocation requires a high degree of accuracy in client location tracking. A recommended cell overlap of 50% ensures that client devices are consistently within the range of multiple access points, which improves location accuracy and reliability. References: CCNP Enterprise Wireless Design ENWLSD 300-425 and Implementation ENWLSI 300-430 Official Cert Guide.

In a hospital setting, the kitchen is a common source of 2.4 GHz RF noise due to the use of microwave ovens which operate on the same frequency. X-ray radiography equipment, while primarily using higher frequency ranges, can also contribute to RF noise in both the 2.4 GHz and 5 GHz bands due to electronic components and shielding inefficiencies. References: CCNP Enterprise Wireless Design ENWLSD 300-425 and Implementation ENWLSI 300-430 Official Cert Guide.

https://www.ciscopress.com/articles/article.asp?p=2351131 &seqNum=2

In a warehouse setting, the height at which access points are installed can significantly impact the wireless signal. If the access points are placed too high, the signal may not adequately reach the users. Additionally, absorption by materials commonly found in warehouses, such as metal racks and goods, can weaken the wireless signal, negatively affecting the users.

https://www.cisco.com/c/en/us/products/collateral/wireless/aironet-1250-series/design_guide_c07-693245.html#_Toc309331086

 When configuring Cisco Prime Infrastructure, to represent the impact of a thick glass wall with an attenuation of 2dB on the RF signal, the obstacle that should be placed in the map editor is glass. This is because the material-specific attenuation values are used to model the RF signal’s behavior as it passes through different types of obstacles, and the thick glass wall’s impact is best represented by the glass obstacle in the map editor.

The issue described indicates that there are more critical priority access points than the backup Cisco WLC can handle with its available licenses. Since there are only 10 licenses available and 7 access points are set to critical priority, not all of them can failover when the primary Cisco WLC is at full capacity. This oversubscription of critical priority access points prevents all of them from failing over as expected.

 The issue described is indicative of a hidden node problem, where MAP-1 and MAP-3 cannot hear each other’s transmissions but can both communicate with RAP-2. This leads to frame collisions as both MAPs may attempt to transmit at the same time, unaware of the other’s actions. The design needs to address this by implementing mechanisms such as RTS/CTS or adjusting the placement of the APs to avoid this issue.

https://www.cisco.com/en/US/docs/solutions/Enterprise/Mobility/emob30dg/WiMesh.pdf

In a mobility group, multiple controllers should be configured with the same virtual IP address to ensure proper roaming. This virtual IP address is used by wireless clients during the roaming process to facilitate seamless mobility between controllers.

 To optimize RF performance across different buildings and user densities: C. Configure AP groups for each area type - This allows for customized settings for APs serving different areas. D. Configure RF profiles for each area type - RF profiles enable the customization of RF parameters to suit the specific needs of each building or area type.

Mobility domains and mobility groups are concepts used in wireless networking to manage client roaming and security contexts. When Wireless LAN Controllers (WLCs) are in the same mobility domain, they can communicate with each other, allowing clients to roam seamlessly between APs managed by different controllers. Mobility groups further refine this by constraining the distribution of a client’s security context, which includes authentication and encryption keys, and by managing AP failover between controllers. This ensures that a client can maintain a secure and stable connection as they move throughout the network.

For an effective office site survey, it’s recommended to: A. Use a battery pack to power APs - This allows for mobility and testing in various locations without relying on fixed power sources. B. Use a drawing of the office space to mark AP and client placements - This helps in planning the optimal locations for AP installation. F. Use APs with built-in antennas - They are commonly used for site surveys as they represent the typical deployment scenario.

For a technology company with multiple buildings requiring seamless wireless coverage, client roaming, and centralized data center with two WLCs (Wireless LAN Controllers) along with core switches, a centralized wireless architecture is most suitable. This architecture allows for easier management of the network from a central location. References := CCNP Enterprise Wireless Design ENWLSD 300-425 and Implementation ENWLSI 300-430 Official Cert Guide Premium Edition and Practice

Voice over wireless roaming is sensitive to delays and interruptions. Full reauthentication, as mentioned in option A, can cause noticeable gaps in a voice conversation because it requires time to re-establish security credentials. This process can interrupt the seamless experience expected in voice communications. Option E is also correct because roaming with only 802.1x authentication indeed requires full reauthentication, which can introduce significant delays affecting voice quality. References: For more detailed information, refer to the CCNP Enterprise Wireless Design ENWLSD 300-425 and Implementation ENWLSI 300-430 Official Cert Guide.

https://www.cisco.com/c/en/us/td/docs/solutions/Enterprise/Mobility/vowlan/41dg/vowlan41dg-book/vowlan_ch5.html

When using the Cisco Prime Infrastructure Planning Tool for deploying a Greenfield 802.11n network with data, voice, location awareness, and APs equipped with WSSI modules, selecting ‘Voice’ will ensure that the tool accounts for the additional bandwidth requirements of voice applications which have strict QoS requirements. Choosing ‘Location’ will allow the tool to consider the need for more precise location tracking capabilities which typically require additional APs for triangulation purposes. References := CCNP Enterprise Wireless Design ENWLSD 300-425 and Implementation ENWLSI 300-430 Official Cert Guide Premium Edition and Practice

 Cisco Hyperlocation requires a dense deployment of access points for accurate location tracking. Adding more APs than a standard site survey suggests can meet the granular location requirements needed for Hyperlocation services. References: ENWLSD official certification guide.

 Adjusting the RX-SOP (Receiver Start of Packet Detection Threshold) can help to control cell size by making APs less sensitive to low-level signals, thus requiring clients to be closer to the AP to connect, which can ensure they connect to the nearest AP with the highest data rates.

In a mobility group design, it is essential that all Wireless LAN Controllers (WLCs) share the same mobility domain name to ensure seamless client mobility and roaming between WLCs. This allows for clients to be recognized across the network and maintain their sessions as they roam. Additionally, when WLCs are in a Stateful Switch Over (SSO) high availability pair, they must use the same virtual IP address to present a single network entity to the wireless clients, ensuring uninterrupted service in the event of a failover.

The issue where APs failed over to the tertiary controller instead of the secondary controller during a controller failure is likely due to the secondary controller being at capacity. When a controller reaches its maximum capacity, it cannot accept any additional APs, causing them to failover to the next available controller in the high availability configuration.

 For supporting hyperlocation, it is recommended that APs be aligned in the same direction. This uniform alignment helps in accurately determining the AP Azimuth, X-Y, and ceiling height information, which is crucial for hyperlocation accuracy and minimizes confusion and user-entered errors.

 LAG-based redundancy is chosen for its ability to provide continuous connectivity as long as one port in the LAG is operational (B), utilize the full bandwidth capacity of all the links in the LAG (E), and allow for the grouping of ports into multiple LAGs for increased redundancy and bandwidth (F). References: CCNP Enterprise Wireless Design ENWLSD 300-425 and Implementation ENWLSI 300-430 Official Cert Guide.

 The redundancy management heartbeat in Cisco Wireless LAN Controllers (WLCs) running 8.x code in Stateful Switch Over (SSO) mode uses UDP packets for communication. When troubleshooting connectivity issues between two WLCs, it is essential to filter for UDP packets in a packet capture to verify the heartbeat communication. The heartbeat packets are sent on a specific UDP port, and filtering for this port can help isolate the heartbeat traffic from other types of traffic in the capture.

 The Cisco 5520 WLC v8.3 requires a base license to use OfficeExtend AP functionality, which allows remote workers to have the same wireless connectivity as they would in an office environment.

The voice readiness tool in Cisco Prime inspects the network against a dBm range that is suitable for voice over Wi-Fi. The range of -72 to -67 dBm is considered optimal for voice applications, ensuring clear audio quality and minimal packet loss.

https://www.cisco.com/c/en/us/td/docs/net_mgmt/prime/infrastructure/34/user/guide/bk_CiscoPrimeInfrastructure_3_4_0_UserGuide/bk_CiscoPrimeInfrastructure_3_4_0_UserGuide_chapter_01010.html

Devices that only support 2.4 GHz can increase congestion on this frequency band, especially in environments where multiple devices are present. This is because the 2.4 GHz band has fewer non-overlapping channels compared to 5 GHz, leading to more interference and potential performance issues.

To focus the coverage heat map on the desired coverage, the engineer should use the RSSI slider to set the heat map to the desired cutoff filter. This action will adjust the display to show only the signal levels that meet or exceed the specified RSSI value, effectively filtering out weaker signals and highlighting areas with sufficient coverage. References: Designing Cisco Enterprise Wireless Networks (ENWLSD 300-425)

 Enabling AP fallback globally on the WLC allows access points to reconnect to their primary controller after they have connected to a secondary controller due to the primary being offline. This ensures that once the primary WLC is back online, APs will revert to it, maintaining the intended primary/secondary controller hierarchy.

In Cisco WLC release 8.9, the controller software can scale up to 20 WLCs and 3000 APs within a single RF group. This capability allows the Radio Resource Management (RRM) algorithms to function effectively across a larger network, optimizing the wireless experience by managing the RF environment and resources across multiple controllers and access points.

For mobility tunnels to come up between WLCs, they need to be part of the same mobility group. If they are configured with different mobility groups, the mobility tunnels will not establish, preventing the WLCs from sharing client, AP, and security information.

For high availability pairing of two Cisco WLCs for client SSO, it is essential that both controllers have the same number of licenses to ensure feature parity and seamless failover. Additionally, they must run the same operating system version to avoid compatibility issues during SSO operations.

 The Cisco Aironet 3800 Series APs support mGig, which allows for higher throughput over existing cabling. However, the maximum cable length that supports 5G operation is limited by the quality of the cable and signal attenuation. Category 5e cabling can support 5G operation up to a length of 130 meters, which is within the acceptable range for maintaining the required signal integrity for 5G speeds.

 In a Layer 1 passive wireless site survey, the chart that indicates the ratio of interference present during the duration of the capture in the 2.4 GHz spectrum is typically a Duty Cycle chart or an Interference chart. These charts display the percentage of time that energy, possibly from interfering sources, is present on a channel. The correct answer would show fluctuations in signal levels over time, highlighting periods where interference might be affecting the channel’s clarity.

 In a wireless network design where redundancy is required for guest access, setting different priorities for the anchor controllers ensures that one serves as the primary and the other as a backup. Anchor A, being the primary controller, should have a higher priority (lower numerical value), making it the preferred choice for guest WLAN connections. Anchor B, as the secondary or backup controller, should have a lower priority (higher numerical value) so that it is used only if Anchor A fails. This approach provides a failover mechanism for guest access in the DMZ.

The exhibit refers to the Cisco Prime Infrastructure’s planning mode feature, which is a tool used for designing and planning wireless networks. The planning mode allows network administrators to input floor plans and simulate access point placement for optimal coverage. It does not require a special license; it is part of the Cisco Prime Infrastructure’s base functionalities. Planning mode does not necessarily present the recommended number of APs; instead, it allows users to manually place potential APs on a map to predict coverage areas. While synchronization with controllers may enhance functionality, it is not strictly necessary for planning mode to operate.

References := (CCNP Enterprise Wireless Design ENWLSD 300-425 and Implementation ENWLSI 300-430 Official Cert Guide Premium Edition and Practice)

To connect multiple wired devices over a workgroup bridge using an autonomous AP, a router is needed to manage the IP addresses and route traffic between the wired devices and the wireless network. The router will act as a gateway for the wired devices, allowing them to communicate with the WLAN. References: Cisco autonomous AP configuration guides and workgroup bridge deployment scenarios.

The Cisco 5520 WLC supports Link Aggregation (LAG), which allows multiple physical interfaces to be treated as a single logical channel. By connecting a second 10-GB interface and implementing LAG, the customer can increase the throughput capacity and provide redundancy without the need for a second controller. This approach also simplifies network design and management by reducing the number of IP addresses needed for the controllers and APs. References: Designing Cisco Enterprise Wireless Networks (ENWLSD) training and certification materials.

To optimize roaming in a wireless network with multiple controllers, it is essential to use the same WLAN name (SSID) across all controllers. This allows clients to roam seamlessly between access points managed by different controllers without having to re-authenticate or experience disconnections1.

 The most effective way to address the issue is to resurvey the areas with the correct survey devices. This ensures that the design accurately reflects the performance characteristics of the specified access points for each area type, leading to a more reliable and efficient wireless network design tailored to each environment’s specific needs.

 In a high-density environment where 5 GHz coverage is provided by nine APs, disabling the 2.4 GHz radios on some APs can reduce co-channel interference because the 2.4 GHz band has fewer non-overlapping channels. This approach helps maintain coverage while mitigating interference.

An RSSI value of -77 dBm is within the range that a 5 GHz radio can receive and decode, provided it’s not below the RX-SOP threshold set for the RF profile. Since the RF profile is set to Medium for 802.11a, which operates in the 5 GHz band, the AP’s 5 GHz radio will decode the frames.

 Changing the TPC Power Threshold to -65 dBm would generally result in a decrease in the transmit power of APs to maintain a smaller cell size. This helps in reducing interference and improving overall network performance. A lower threshold means the APs reduce their power to ensure the signal does not exceed -65 dBm, leading to decreased signal strength at the client side.

The command debug mobility handoff enable is used to validate the mobility control packets between Wireless LAN Controllers (WLCs). This command enables debugging of the handoff process, which is critical for ensuring seamless client roaming between controllers. When WLCs are separated by firewalls, it is essential to confirm that mobility control packets can traverse these firewalls without being dropped or rejected. The debug mobility handoff enable command allows network administrators to monitor the handoff process and troubleshoot any issues that may prevent successful client roaming.

The ‘eping’ command is used on Cisco Wireless LAN Controllers to verify that the redundancy peer in a Stateful Switchover (SSO) pair of controllers is up and connected. This command sends ECHO packets to the peer controller to ensure connectivity.

AP Fallback is a feature that allows APs to rejoin their primary controller after they have connected to a secondary controller due to a failure. By enabling AP Fallback on the primary controller, the APs will automatically rejoin it when it becomes available again after a power interruption. This ensures that APs return to their designated primary controller for normal operations.

By segmenting the VLAN into smaller subnets and assigning them by location, an engineer can use interface groups. This allows for efficient management of network resources and ensures that clients are connected to the closest subnet, reducing latency and improving performance.

 For Stateful Switchover (SSO) to function correctly, the redundancy ports on both the primary and secondary controllers must be directly connected. This allows for the necessary state and configuration information to be synchronized between the two controllers, preventing the secondary controller from entering maintenance mode in the event of a failover.

In Cisco WLC version 8, the need for separate WPlus licenses has been eliminated as all features that were previously part of the WPlus license are now included in the Base license. This consolidation simplifies licensing management and ensures that customers have access to all necessary features without requiring additional licenses. References := (CCNP Enterprise Wireless Design ENWLSD 300-425 and Implementation ENWLSI 300-430 Official Cert Guide Premium Edition and Practice)

To mitigate increased co-channel interference and retransmissions after adding an AP, Transmit Power Control (TPC) and Dynamic Channel Assignment (DCA) can be effective. TPC adjusts AP transmit power based on real-time analysis of the wireless environment, reducing interference by lowering power where necessary. DCA dynamically changes channel assignments based on current RF conditions to optimize performance and minimize interference.

 For mobility tunneling through a firewall in a Cisco wireless network environment, UDP port 16666 must be open along with IP Protocol number ‘97’, which is used for Encapsulating Security Payload (ESP) traffic typically found in IPsec tunnels. By ensuring these ports are mapped correctly through the firewall, R&D engineers can roam within their department while maintaining a secure mobility tunnel. References := (CCNP Enterprise Wireless Design ENWLSD 300-425 and Implementation ENWLSI 300-430 Official Cert Guide Premium Edition and Practice)

Micro cells with reduced power levels are suitable for environments with a high concentration of wireless clients and multimedia applications, as they help manage interference and allow for better roaming capabilities. References: ENWLSD 300-425 Official Cert Guide.

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 Enabling control plane encryption on the wireless controller is crucial for establishing a secure mobility tunnel between the wireless controller and the anchor controller. Control plane encryption ensures that the signaling and management traffic traversing the mobility tunnel is encrypted, providing a secure channel for guest access authentication and authorization processes. This is particularly important when the anchor controller is deployed within a DMZ, as it is exposed to potential external threats. The Cisco Catalyst 9800 Series wireless controller supports control plane security features that can be leveraged to secure the mobility tunnel and ensure the integrity and confidentiality of the control traffic.

 Metal doors cause the most signal attenuation in wireless design due to the properties of metal reflecting and absorbing radio waves, which can significantly reduce signal strength. Unlike materials such as cinder block or glass, metal can create a complete barrier for the signal, leading to a phenomenon known as “Faraday Cage” effect, where the metallic enclosure blocks electromagnetic fields. References: Designing Cisco Enterprise Wireless Networks (ENWLSD 300-425)

: Band Select is a feature on Cisco Wireless LAN Controllers (WLC) that encourages dual-band wireless clients to connect to the less congested 5 GHz band. This helps to balance the client load between 2.4 GHz and 5 GHz and improve overall network performance in high-density environments.

When a client roams between two access points (APs) that are registered to different controllers with interfaces in the same client subnet, the controllers will exchange mobility control messages over UDP port 16666. This is in accordance with the Designing Cisco Enterprise Wireless Networks (ENWLSD) guidelines. The purpose of these messages is to ensure seamless roaming, where the client’s session and authentication state are transferred from one controller to another without requiring re-authentication or re-association by the client. The mobility control messages facilitate the coordinated transfer of the client database entry from the original controller to the new one, maintaining a consistent experience for the user.

When designing a wireless network for diverse clients, it’s crucial to ensure that the network will be reliable for all users. Therefore, surveys should be conducted with the client that has the worst RF characteristics, as indicated in option D. This approach ensures that the network is designed to support even the weakest client, thereby providing a consistent experience for all users. 

https://documentation.meraki.com/MR/WiFi_Basics_and_Best_Practices/Conducting_Site_Surveys_with_MR_Access_Points

Receiver Start of Packet Detection Threshold (RxSOP) helps to mitigate high-channel utilization by ignoring rogue APs and other RF interference sources. By adjusting the RxSOP threshold, APs can be made less sensitive to unwanted signals, thus reducing the impact of interference. References: CCNP Enterprise Wireless Design ENWLSD 300-425 and Implementation ENWLSI 300-430 Official Cert Guide.

The WPlus license is suitable for environments using OfficeExtend Access Points (OEAP), which allows employees to work from home with a seamless connection to the corporate wireless network. The WPlus license enables features such as advanced security and increased scalability for remote workers. References: CCNP Enterprise Wireless Design ENWLSD 300-425 and Implementation ENWLSI 300-430 Official Cert Guide.

Jammers are non-Wi-Fi interferers that can be identified by Metageek Chanalyzer. They intentionally disrupt wireless communications by emitting radio frequencies that interfere with Wi-Fi signals. Chanalyzer is designed to detect such patterns of interference.

https://www.metageek.com/training/resources/wifi-and-non-wifi-interference

For a cost-effective high availability deployment in a campus enterprise wireless network with three controllers, the N+1 architecture with Stateful Switch Over (SSO) is recommended. This architecture provides redundancy and allows for seamless failover without service interruption, ensuring that the network remains highly available without the need for a one-to-one controller redundancy, which would be less cost-effective

https://www.cisco.com/c/en/us/td/docs/wireless/technology/hi_avail/N1_High_Availability_Deployment_Guide/N1_HA_Overview.html?