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

 Cisco FastLocate technology is part of the Cisco Hyperlocation solution, which enhances location tracking accuracy and refresh rates. Implementing Cisco FastLocate technology can address issues with refresh rates for location updates in a custom mobile app by increasing the number of location data points captured, thus providing more frequent and accurate location updates.

References := AP4800 Hyperlocation Deployment Guide - Cisco

 Mobility groups are created by configuring each Wireless LAN Controller (WLC) to use the same mobility domain name and defining each WLC as a peer in the static mobility members list of every other WLC in the group. This configuration allows WLCs to share information and support seamless roaming for wireless clients across different controllers within the same mobility group.

References := Chapter: Chapter 14 - Configuring Mobility Groups - Cisco

 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.

 Optimized roaming is a feature that helps manage the client’s roaming behavior by disassociating clients with a signal strength below a predefined threshold. This feature is designed to prevent clients from sticking to an AP with poor connectivity, which can lead to suboptimal performance. If the BSS Transition Management query is causing the client to roam and the disassociation imminent feature is not enabled, it indicates that optimized roaming is likely enabled, prompting the client to seek a better AP connection.

 Cisco 3800 Series APs support higher speeds provided by IEEE 802.11ac Wave 2, which Fast Ethernet switches cannot fully support. Replacing them with mGig or gigabit switches with 10G uplinks will ensure the infrastructure can handle the increased data rates. The CAT 6A standard supports these speeds, so there’s no need to replace the wiring if it’s already CAT 6A.

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 IEEE 802.11r protocol, also known as Fast BSS Transition (FT), is designed to support real-time applications by enabling faster roaming between APs. This protocol reduces the number of packets exchanged during the reauthentication process when a client moves from one AP to another, thus ensuring a more seamless transition and maintaining the quality of service required by real-time applications such as voice and video conferencing. References: Designing Cisco Enterprise Wireless Networks (ENWLSD 300-425)

 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.

In Cisco wireless networks, access points can be configured with failover priorities ranging from 1 to 4, with 1 being the highest priority and 4 being the lowest. An access point with priority 1 is considered critical and will be given preferential treatment in failover situations, ensuring that it reconnects to a backup controller before access points with lower priorities

 In an outdoor mesh network designed to cover sports fields, a 5 GHz, 14-dBi patch antenna is suitable for the RAP for backhaul connectivity. The higher gain and directional nature of a patch antenna help in focusing the signal over longer distances and in specific directions, which is ideal for connecting various points in a large outdoor area5.

https://www.cisco.com/c/en/us/products/collateral/wireless/aironet-antennas-accessories/product_data_sheet09186a008008883b.html

 The design approach should use the 5 GHz frequency band without channel bonding to support 20 MHz channels. This provides a balance between network capacity and interference mitigation.

https://www.cisco.com/c/en/us/support/docs/wireless/4400-series-wireless-lan-controllers/108184-config-802-11n-wlc.html

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.

 Fast Transition (FT), also known as IEEE 802.11r, is the key-caching mechanism that must be configured to speed up the reauthentication delays on the wireless infrastructure. FT allows for rapid re-authentication when roaming between access points, reducing the time required for re-establishing security keys and thus speeding up the overall process2.

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 collapsing all controllers to a single cluster in a central location, one must consider the availability of channels across different regions. Regulatory domains vary globally, and certain channels allowed in Europe may not be available or legal in other parts of the world. This can affect the consistency of wireless coverage and performance.

https://www.cisco.com/c/en/us/td/docs/wireless/controller/technotes/86/b_Cisco_Wireless_LAN_Controller_Configuration_Best_Practices.html

In a global mesh deployment, using redundant controllers in the least restrictive regulatory domain ensures the highest number of channels available for backhaul. This design accommodates the varying regulatory constraints of different regions by adhering to the domain with the most lenient channel availability.

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.

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.

 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.

 Cisco FlexConnect mode is designed for branch offices that lack a wired backhaul. It allows APs to switch client data traffic locally while still performing client authentication centrally. This mode provides the flexibility needed for branch deployments, ensuring that client traffic is handled efficiently even if the WAN link to the central site is down. References: Cisco FlexConnect technical documentation and Designing Cisco Enterprise Wireless Networks (ENWLSD) training.

For seamless roaming between access points, the protocol that supports fast transitions is 802.11r. This amendment to the 802.11 standard allows devices to roam quickly by establishing security credentials before moving to the next access point, reducing the time required for reauthentication.

 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.

Voice services on a wireless network require a strong and stable signal, as well as low interference and retransmission rates. An RSSI (Received Signal Strength Indicator) of at least -67 dBm is considered the minimum for acceptable voice quality, and -65 dBm is even better, providing a buffer for signal fluctuation. A noise floor of -87 dBm would be too high and could interfere with signal clarity. Retransmission rates should be kept as low as possible; 15% or below is a good target to ensure efficient communication.

References: CCNP Enterprise Wireless Design ENWLSD 300-425 and Implementation ENWLSI 300-430 Official Cert Guide

 In a mining facility, especially within mine shafts where the environment can be long and narrow, an omnidirectional antenna is typically used for a Layer 2 survey. This type of antenna radiates RF signal equally in all directions, providing coverage along the length of the shaft.

 A fully measured wireless survey requires tools that support the active functioning of the network and allow for physical access to install and measure equipment. A PoE (Power over Ethernet) battery is necessary to power the access point during the survey. The access point itself is essential for broadcasting the signal. A ladder is needed to reach high places for proper access point placement and to measure coverage areas effectively.

References: CCNP Enterprise Wireless Design ENWLSD 300-425 and Implementation ENWLSI 300-430 Official Cert Guide

https://www.cisco.com/c/en/us/td/docs/wireless/technology/mesh/81/design/guide/b_mesh_81/Site_Preparation_and_Planning.html

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)

 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.

The Catalyst 9300X-48HX switches support PoE, which can power the 9166 APs. To ensure that all APs run with full functionalities, including PoE, the engineer should connect the APs to all available ports on the stack of two Catalyst 9300X-48HX switches. This will provide sufficient power and connectivity for the APs to operate effectively. References: Cisco Catalyst 9300X switch specifications and PoE requirements for 9166 APs.

 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.

Typically, a Cisco workgroup bridge can support up to 20 wired client connections. This allows for a reasonable number of devices to be connected while maintaining performance.

https://www.cisco.com/c/en/us/td/docs/wireless/controller/7-4/configuration/guides/consolidated/b_cg74_CONSOLIDATED/b_cg74_CONSOLIDATED_chapter_010100001.html

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.

In a medical treatment environment where both data and voice services are required, continuous coverage of -67 dBm from one access point is the minimum requirement. This ensures that there is sufficient signal strength for reliable voice communication, which is critical in medical settings. The -67 dBm threshold is commonly recommended for voice applications to ensure call quality and reliability.

So -67dBm covers both Data & Voice with a single AP

 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.

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

 When designing a network with a DMZ and an EoIP tunnel, it’s important to ensure that the data plane is encrypted to protect the data as it traverses potentially unsecured networks. Cisco IOS-XE on the Catalyst 9800 supports encryption of the data plane, which is essential for this design.

 Creating AP groups for each location allows for the mapping of specific VLANs to an internal SSID tailored for that area. This approach enables clients to be on different subnets based on their building location within a single controller environment.

https://www.cisco.com/c/en/us/support/docs/wireless-mobility/wireless-vlan/71477-ap-group-vlans-wlc.html

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)

 In the scenario described, where some APs did not failover to their secondary controller despite having sufficient licenses, the issue likely lies with the configuration of the APs to recognize the secondary controller. Since the controllers are not in a mobility group but have A records for their hostnames in DNS, this suggests that they rely on DNS for AP discovery and failover. If APs are not failing over as expected, it could be due to an incorrect IP address configured for the secondary controller on the AP or within DNS. The exhibit shows that the “Secondary Controller” field has an IP address of “10.42.89.11”, which should be verified against DNS records and actual controller settings to ensure accuracy. References := (CCNP Enterprise Wireless Design ENWLSD 300-425 and Implementation ENWLSI 300-430 Official Cert Guide Premium Edition and Practice)

 AP groups allow the mapping of specific WLANs (SSIDs) to distinct VLANs for different locations. This design enables clients to be on different subnets based on their building location without modifying the access points’ mode of operation.

 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.

 The concern with existing gigabit uplinked switches providing 802.3at is the output power limitation. 802.11ac Wave 2 APs may require more power than what 802.3at can deliver, especially for features like Multi-User Multiple Input Multiple Output (MU-MIMO). References: CCNP Enterprise Wireless Design ENWLSD 300-425 and Implementation ENWLSI 300-430 Official Cert Guide.

Link Aggregation Group (LAG) allows multiple physical ports to be combined into a single logical channel. In the scenario where only one Cisco 9800-40 WLC is available and high availability is required, LAG can be used to manage port redundancy and perform load balancing between APs transparently. This ensures that if one cable fails, the others can continue to carry the traffic without any perceived downtime

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

 In an auditorium seating 500 students with laptops, a high-density design model is appropriate. This model focuses on supporting a large number of devices in a concentrated area with sufficient coverage and bandwidth. It involves strategic AP placement, proper channel planning, and capacity planning to ensure all students have reliable wireless access. References: CCNP Enterprise Wireless Design ENWLSD 300-425 and Implementation ENWLSI 300-430 Official Cert Guide Premium Edition and Practice

https://www.cisco.com/c/dam/en_us/solutions/industries/docs/education/cisco_wlan_design_guide.pdf

To address aesthetic concerns, using enclosures can effectively conceal wireless infrastructure, such as access points, within the environment. This helps maintain the visual appeal of the area while still providing the necessary wireless coverage.

The 5 GHz band is recommended for voice over wireless due to its wider channel bandwidths, allowing for higher data rates. Setting the cell boundary at -67 dBm ensures sufficient signal strength for reliable voice communication. References: CCNP Enterprise Wireless Design ENWLSD 300-425 Official Cert Guide.

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.

The Voice Readiness tool within Cisco Prime Infrastructure is designed to assess the wireless network’s ability to support voice services, including VoIP. It evaluates various factors such as signal strength, noise levels, and coverage to ensure that the wireless network can handle the quality of service requirements needed for voice communications.

For wireless clients to use the 5 GHz band when Client Band Select is enabled, certain conditions must be met. Channel bonding should be enabled on the WLAN to allow for wider channels, providing higher throughput available in the 5 GHz band. The client must receive an RSSI above the minimum threshold set for Band Select to steer them towards the 5 GHz band. Additionally, the client device must be dual-band capable to connect to both 2.4 GHz and 5 GHz bands. Co-channel interference levels and UNII-2 extended channels being enabled offer additional benefits but are not requirements for Band Select functionality. Having 802.11a enabled on WLAN is necessary for any operation on the 5 GHz band but does not specifically relate to ensuring clients use this band under Band Select policies.

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

For a high-density WLAN environment like a 10,000-seat auditorium, placing APs under the seats can take advantage of human attenuation and maintain the aesthetics of the room. Human bodies absorb Wi-Fi signals, and placing APs under the seats helps in mitigating this effect by having the signals emanate from among the audience, rather than from above where the signals would have to pass through the audience, resulting in signal degradation1.

 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

A Patch antenna should be used to provide wireless coverage on the perimeter of a building while minimizing signal leakage. Patch antennas have a directional radiation pattern that can be focused along the perimeter.

https://www.cisco.com/c/en/us/td/docs/routers/connectedgrid/antennas/installing-combined/industrial-routers-and-industrial-wireless-antenna-guide/ANT-MP-INT-OUT-M.html

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.