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

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.

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

 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.

To reduce co-channel interference, it’s beneficial to decrease channel bonding, which will increase the number of non-overlapping channels available. Reducing the power of the APs can also help minimize interference by reducing the range of each AP’s signal, thereby reducing the chance of overlap.

The ‘tracert’ command is used to test connectivity between members of a mobility group by tracing the path that mobility control packets take over the network. This command helps identify any potential issues with the route that the packets are taking, which could affect the ability of guests to connect to the anchor controller in the DMZ. References := (CCNP Enterprise Wireless Design ENWLSD 300-425 and Implementation ENWLSI 300-430 Official Cert Guide Premium Edition and Practice)

 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.

 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

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

 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.

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.

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.

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

To reduce full authentication requests and optimize roaming, enabling Cisco Centralized Key Management (CCKM) on the voice SSID is effective. CCKM allows for fast re-authentication during roaming, which is beneficial for voice applications. Adding APs to a FlexConnect group helps manage APs in remote branches more efficiently.

 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.

 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.

References:

• CCNP Enterprise Wireless Design ENWLSD 300-425 Official Cert Guide

https://www.cisco.com/en/US/docs/solutions/Enterprise/Mobility/emob30dg/RFDesign.html#wp1000551

FlexConnect mode is ideal for branch offices and remote locations where it’s necessary to minimize wireless traffic tunneled back to the Wireless LAN Controller (WLC). In FlexConnect mode, APs can perform client authentication locally and bridge traffic onto the local network. References: CCNP Enterprise Wireless Design ENWLSD 300-425 and Implementation ENWLSI 300-430 Official Cert Guide.

The data path issue between the Cisco Catalyst 9800-CL and AireOS 5520, despite an active control path, is likely due to encrypted mobility being enabled on the AireOS 5520. Encrypted mobility requires both peers to have a matching configuration for encryption, which includes proper certificates and shared secrets. If there’s a mismatch, the control path may be established, but the data path can fail due to the inability to establish an encrypted tunnel.

 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.

 For mobility between two buildings with one controller at each site, CAPWAP data and control traffic must be able to pass between controllers. CAPWAP control messages use UDP port 5246 while CAPWAP data messages use UDP port 5247; therefore, these ports must be open to allow inter-controller communication for seamless mobility. References := (CCNP Enterprise Wireless Design ENWLSD 300-425 and Implementation ENWLSI 300-430 Official Cert Guide Premium Edition and Practice)

 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

When configuring high availability on an access point, a network engineer can configure a maximum of two controllers. One serves as the primary controller, and the other serves as the secondary controller.

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When designing anchor redundancy for guest clients with auto-anchor configured on a WLC running version 8.1 or above, setting up Guest Anchor Priority ensures that one anchor is treated as active while another acts as standby rather than load-balancing clients between anchors which is not desired in this case. References := (CCNP Enterprise Wireless Design ENWLSD 300-425 and Implementation ENWLSI 300-430 Official Cert Guide Premium Edition and Practice)

 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.

 To ensure that the most critical APs at remote sites remain functional in the event of a failure, the Global AP Failover Priority feature can be used. By setting the priority of the most important APs to “critical”, these APs will be given precedence over others during a failover scenario. This allows the engineer to prioritize which APs should remain online without impacting the main site’s APs, which are set to a “high” priority.

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

When identifying network requirements, it’s important to consider the number of wireless devices that will need access to ensure sufficient capacity and coverage. The business type can influence the types of applications and services that will be used, which in turn affects the network 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

 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.

The 9800 Series Wireless Controller uses CAPWAP tunnels to encapsulate and transport both control and data traffic between access points and the controller. This allows for centralized management and control while also enabling efficient data forwarding.

https://www.cisco.com/c/en/us/td/docs/wireless/controller/9800/config-guide/b_wl_16_10_cg/mobility.html

The Cisco AIR-2702i AP can be set to various modes for different purposes. For conducting a Layer 1 site survey to discover non-Wi-Fi interference, the AP should be set to Monitor mode. In this mode, the AP can scan the radio environment for interference sources without serving any clients, making it ideal for use with tools like Metageek Chanalyzer.

References: Designing Cisco Enterprise Wireless Networks (ENWLSD) 300-425 Official Cert Guide

 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)

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)

Raising the minimum data rate to 24 Mbps will reduce the range at which devices can connect, thereby reducing channel overlap. Using directional antennas can also help limit the coverage area of some APs, which can further reduce channel overlap by focusing the signal in specific directions rather than in a broad coverage pattern. References: Designing Cisco Enterprise Wireless Networks (ENWLSD 300-425)

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.

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

 In a high-availability configuration, orphaned APs will join the controller with the lowest percentage of associated Access Points (APs) per license capacity by default. This ensures a balanced distribution of APs across the controllers in the mobility group, optimizing resource utilization and network performance. References: Designing Cisco Enterprise Wireless Networks (ENWLSD 300-425)

In high-density environments, such as stadiums or auditoriums, APs are often mounted under the seats to provide a controlled cell size with attenuation. This placement helps to manage the RF environment by providing attenuation of 6 dB to 20 dB, which can reduce co-channel interference and improve the user experience by ensuring a strong signal and minimizing noise from other cells.

For predictive designs, especially for location readiness and interference mitigation, a mid-range power level like 18 mw is often used. It provides a balance between coverage and minimizing interference with other devices and networks.

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.

To support a high density of mobile devices and bond channels in groups of two, the channel width for 802.11a should be set to 40 MHz. Setting the data rates to 24 MB and Mandatory ensures that only APs can send 802.11 management frames at this rate, which helps in managing the airtime fairness. References: CCNP Enterprise Wireless Design ENWLSD 300-425 and Implementation ENWLSI 300-430 Official Cert Guide.

 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

 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.

 Smartphones and tablets typically have fewer antennas than laptops, which can affect their signal reception and transmission capabilities. Additionally, they often support lower data rates compared to laptops due to their smaller size and power constraints.

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 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 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.

 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.

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.

 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.

 Mobility tunnels between Cisco Wireless LAN Controllers (WLCs) use UDP port 16666 for control messages and UDP port 16667 for data traffic. If EPING is failing, it indicates that the necessary ports are not open. Allowing UDP port 16666 through the firewall would enable the control messages required for establishing the mobility tunnels.

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 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.

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.

 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.

 When a data path mobility tunnel fails to come up, one of the troubleshooting steps is to check if the necessary ports are open and not being blocked by any firewalls in the path. Since the mobility tunnel uses CAPWAP, which operates on UDP ports 16666 (control path) and 16667 (data path), establishing a Telnet connection to the firewall on port 16666 can help determine if the control path is open and if there are any issues that need to be addressed3.