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

For pervasive coverage in an oil terminal that supports casual web and email traffic over 5 GHz, disabling lower data rates can help improve overall network efficiency. Lower data rates can cause the network to slow down because they take up more airtime. By disabling rates below 24 Mbps, the APs can focus on providing higher throughput for users. Keeping the power assignment as auto allows the APs to adjust their power levels dynamically for optimal coverage and client performance

 The connectivity of 802.11a, which operates in the 5 GHz band, is reduced in X-ray rooms primarily due to the increased signal attenuation caused by the lead and other dense materials used in the construction of these rooms to shield against X-ray radiation. These materials effectively block or weaken the radio signals used for wireless communication

portable X-ray machines, sending high-resolution images, sometimes in real time, echography machines, and electrocardiography [ECG] machines). These devices may also use the same spectrum as Wi-Fi but with other protocols and, therefore, become sources of interference for your system.

 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.

A centralized wireless architecture is suitable for a college with multiple buildings. It allows for centralized management of WLCs and supports seamless roaming for wireless clients across different APs and controllers.

https://www.cisco.com/c/en/us/td/docs/solutions/Enterprise/Mobility/emob41dg/emob41dg-wrapper/ch2_Arch.html

 During a client roaming event, the Wireless LAN Controller (WLC) is responsible for communicating the new Layer 2 Endpoint ID (EID) mapping of a wireless supplicant to the fabric domain. The WLC acts as a mobility orchestrator within the Cisco Digital Network Architecture (DNA) to ensure seamless roaming and connectivity. References: Designing Cisco Enterprise Wireless Networks (ENWLSD 300-425)

https://www.cisco.com/c/dam/en/us/td/docs/cloud-systems-management/network-automation-and-management/dna-center/deploy-guide/cisco-dna-center-sd-access-wl-dg.pdf

The IEEE 802.11k protocol is designed to enable radio resource measurement and neighbor list radio management packets. This protocol allows wireless devices to better understand their radio environment, which in turn supports real-time applications over wireless by enabling devices to make quicker and more informed decisions about roaming

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.

 RXSOP (Receive Start of Packet Detection Threshold) and TPC (Transmit Power Control) are two features that can help manage the challenges associated with a high AP (Access Point) count in a dense environment like a university auditorium. RXSOP can be adjusted to refine how APs differentiate between noise and valid packets, which is particularly useful in high-density areas where multiple APs might otherwise respond to the same signal. TPC helps in managing the transmit power of APs, allowing for better coverage and reduced interference among APs that are in close proximity to each other. References: Designing Cisco Enterprise Wireless Networks (ENWLSD 300-425)

https://www.cisco.com/c/en/us/support/docs/wireless-mobility/80211/200069-Overview-on-802-11h-Transmit-Power-Cont.html

In a high availability setup with Cisco 5508 Wireless LAN Controllers, the standby controller can be accessed via the console connection and the service port interface. The console provides direct access, while the service port interface allows for network-based access to the standby unit for management purposes.

When the mobility tunnel is not operational for the data path, it is essential to validate the network’s firewall settings. Firewall port 16666 must be open to allow mobility control messages to pass through, and firewall IP protocol 97 (EtherIP) must be permitted to enable the encapsulation of IP within IP, which is necessary for the data path of the mobility tunnel. Ensuring these firewall settings are correctly configured is critical for facilitating inter-controller roaming and operational mobility tunnels.

The data path being down while the control path is up indicates an issue with the data plane security configuration. The data-dtls setting on the AireOS 5520 WLC is responsible for enabling Datagram Transport Layer Security (DTLS) for the data plane, which encrypts the data traffic between the controllers. If this setting is disabled, the data path cannot be established securely, leading to the observed issue. Therefore, enabling data-dtls on the AireOS 5520 WLC is necessary to resolve the data path downtime.

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.

 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

 Frequent disconnections may occur if the RSSI threshold set for optimized roaming is too high, causing clients to attempt roaming too late. Disabling optimized roaming and enabling 802.11v support allows for better client steering by the AP, as 802.11v includes the BSS Transition Management feature, which guides clients to a better AP based on the network’s conditions.

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.

 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.

: 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.

Optimized roaming is a feature that helps mitigate sticky client behavior by assessing the client’s signal strength and proactively disconnecting clients with a signal below a predefined threshold. This encourages clients to connect to a closer AP with a stronger signal, improving the overall wireless experience in high-density areas.

https://www.cisco.com/c/en/us/td/docs/wireless/controller/technotes/80/hdx_final/b_hdx_dg_final/high_density_experience_features_added_in_release_8_0.html

Quality of Service (QoS) is essential for prioritizing cloud services like email and real-time communication. It helps in managing bandwidth allocation and ensuring that critical applications receive the necessary resources for optimal performance.

https://community.cisco.com/t5/wireless-mobility-documents/what-is-cckm-and-how-does-it-affect-fast-and-secure-roaming/ta-p/3130421

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.

 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.

 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.

 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)

 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.

 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

When conducting a Layer 2 site survey, it is recommended to match the survey to the worst client available. This ensures that the wireless network is designed to provide adequate coverage and performance even for the clients with the poorest capabilities, thereby ensuring a consistent user experience for all devices2.

https://www.cisco.com/c/en/us/support/docs/wireless/5500-series-wireless-controllers/116057-site-survey-guidelines-wlan-00.html

For a point-to-multipoint mesh network site survey, configuring the Rx power and Tx power is essential. Rx power will determine the sensitivity of the AP to incoming signals, which is crucial for understanding the reach of each mesh point. Tx power settings will influence the strength of the signals transmitted from the AP, affecting the network’s overall coverage. References: Designing Cisco Enterprise Wireless Networks (ENWLSD 300-425)

In a Cisco wireless network, when designing for client roaming between access points (APs) that are connected to different controllers, especially in a global enterprise with multiple data centers, it is essential to ensure seamless client mobility. Mobility lists are used in such scenarios to define which controllers are allowed to participate in client roaming. This feature allows the APs connected to controllers within one group (e.g., Group ABC) to recognize and facilitate roaming clients from another group (e.g., Group XYZ). The mobility list is configured on each controller and includes the IP addresses of other controllers that should be considered part of the same mobility domain. When a client roams from an AP on one controller to an AP on another controller, if both controllers are in each other’s mobility list, they will establish a mobility tunnel through which they exchange the client’s context and security credentials. This ensures that the client can roam without re-authentication and maintains session continuity.

The survey model described is used for location services, VoIP, data, and video. The placement of APs on exterior walls, building corners, and major turns helps ensure consistent coverage and signal strength for a variety of applications, including precise location tracking and high-quality voice and video communications. References: Designing Cisco Enterprise Wireless Networks (ENWLSD 300-425)

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 decision to avoid installing APs directly in offices is likely due to transmit power considerations. Placing APs within offices could lead to excessive coverage for small areas, causing interference with other APs and reducing overall network performance. By placing them in common areas like corridors, engineers can ensure more uniform coverage across larger spaces while managing transmit power more effectively for optimal performance.

 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

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.

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.

When conducting an outdoor bridge site survey, weather and the Fresnel zone are critical criteria to consider. Weather can affect signal propagation and the reliability of the wireless link, while the Fresnel zone relates to the elliptical area around the line-of-sight path between transceivers, which must be clear of obstacles to ensure a strong signal. References: Designing Cisco Enterprise Wireless Networks (ENWLSD 300-425)

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 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.

 For a government agency requiring high security between device communications, enabling Mobility Encryption across the network is essential. Mobility Encryption enhances the security of the mobility group by encrypting the traffic exchanged between mobility peers, including AireOS, Cisco IOS-XE controllers, and Cisco 4800 Series APs. This encryption helps to protect against potential eavesdropping and unauthorized access, ensuring that sensitive government data remains confidential during wireless transmission.

FlexConnect APs must be in a FlexConnect group to support 802.11r Fast Transition (FT). This grouping allows for local authentication and key management, which are necessary for fast roaming methods that improve voice quality and wireless IP phone performance during roaming.

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)

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

 Devices that can tolerate at most 100 ms of delay when roaming are typically voice devices. Voice applications are sensitive to delays, and ensuring a maximum of 100 ms delay is a common design criterion for a wireless network supporting voice services. References: Designing Cisco Enterprise Wireless Networks (ENWLSD 300-425)

To support high availability, the design must include redundant Wireless LAN Controllers (WLCs) to ensure service continuity in case of a failure. Additionally, having a high availability pair with one WLC holding a valid AP count license ensures that all APs can remain connected and services continue without interruption during failover.

https://www.cisco.com/c/en/us/td/docs/wireless/controller/technotes/7-5/High_Availability_DG.html#pgfId-44074

Setting AP fallback to disabled will prevent the AP from moving back to its defined Cisco WLCs automatically after failing over to an undefined controller. This allows manual intervention to determine when the AP should revert to its primary controller.

 For a WLAN design that supports services like internet, email, voice, and database access, a signal strength of -67 dBm is considered good for voice and streaming services. A 25-dB SNR (Signal-to-Noise Ratio) is also desirable for high-quality voice and video applications, and a maximum of 1 percent packet loss is acceptable to ensure reliable connectivity and service quality.

https://www.cisco.com/c/en/us/support/docs/wireless/5500-series-wireless-controllers/116057site-survey-guidelines-wlan-00.html

 The wireless architecture described is a centralized deployment. This is characterized by access points distributed across multiple buildings and managed centrally by Wireless LAN Controllers (WLCs). Centralized deployments are common in larger environments like a technology company campus because they allow for centralized management, scalability, and advanced features such as load balancing and fault tolerance.

 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.

To support VoWLAN services and provide roaming recommendations to supported voice clients without impacting non-VoWLAN clients, the feature that should be enabled on the VoWLAN SSID is 802.11k neighbor lists. This feature allows APs to provide information about neighboring APs that are candidates for roaming, which helps clients make better decisions about when and where to roam. References := CCNP Enterprise Wireless Design ENWLSD 300-425 and Implementation ENWLSI 300-430 Official Cert Guide Premium Edition and Practice

When conducting site surveys for WLAN upgrades to 802.11n, it’s important to consider AP locations that allow for easy access. This facilitates quick maintenance and upgrades, ensuring minimal downtime and disruption to the network. While aesthetics and power availability are also considerations, the primary focus should be on maintaining the network’s performance and reliability.

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.

Band Select is a feature on Cisco WLCs that encourages dual-band capable clients to connect to the less congested 5 GHz spectrum. It works by delaying the response to clients’ probes on the 2.4 GHz band, making the 5 GHz band more attractive to the client devices.

To minimize channel utilization and interference with existing tenant networks, it’s best to use the UNII-1 channels, which are typically less congested, and stick to 20-MHz channels to provide more non-overlapping channels and reduce co-channel interference.

For handheld mobile scanners processing credit card payments, security and seamless roaming are critical. The 802.11w standard, also known as Protected Management Frames (PMF), provides enhanced security that helps prevent disconnections and issues when roaming between access points. Incorporating 802.11w in the design ensures that the scanners maintain a secure and consistent connection while moving throughout the environment. References: CCNP Enterprise Wireless Design ENWLSD 300-425 and Implementation ENWLSI 300-430 Official Cert Guide Premium Edition and Practice

 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.

The decision to configure LAG-based redundancy is influenced by the following features:

B. All interface traffic passes as long as one port is up: This ensures that the wireless LAN controller can continue to operate and manage traffic as long as at least one port in the LAG is functioning, providing a robust failover solution1.

D. Interface connection to two separate nonstacked switches is available: LAG allows for connections to multiple switches, which can provide redundancy and higher availability compared to single switch connections1.

E. Full bandwidth of all links is available: With LAG, the combined bandwidth of all active ports is available, enhancing the throughput capabilities of the wireless LAN controller1.

 VLAN Select is a feature that allows for the assignment of clients to different VLANs based on various criteria, such as user credentials or device type. In a centralized wireless deployment with N+1 high availability, incorporating VLAN Select can ensure that clients maintain consistent IP addressing across failovers, preventing them from being assigned IP addresses from a different subnet.