300-425 Questions and Answers

 To ensure the anchored traffic remains up if a single WLC in the high-availability cluster fails, the mobility MAC address for the high-availability cluster should be configured. This allows the APs to recognize the cluster as a single entity, maintaining the CAPWAP tunnel to the anchor WLC in the DMZ even if one of the WLCs in the cluster fails.

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.

 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.

 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 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

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

 To predict the number of APs needed to support approximately 300 wireless devices on a new floor with an 802.11ac network, the Demand Settings in the Cisco Prime Infrastructure Planning Tool must be adjusted. This setting allows the planner to specify client density and throughput requirements, which are crucial for determining the correct number of APs.

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.

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.

The human body can attenuate a wireless signal by approximately 6 dB. This is due to the water content in the human body, which absorbs and reflects radio frequency signals, leading to a reduction in signal strength as it passes through or around a person. This factor is important to consider in wireless network design, especially in environments with high user density.

 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.

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

 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.

References:

• CCNP Enterprise Wireless Design ENWLSD 300-425 and Implementation ENWLSI 300-430 Official Cert Guide Premium Edition and Practice Tests

 To maintain the same VLAN and IP address for users roaming between APs attached to different WLCs, a mobility group should be created between WLC-A and WLC-B. This allows for inter-controller roaming, where client sessions are maintained across different controllers, ensuring that users can move across the campus without losing connectivity or changing IP addresses.

References:

• Cisco’s official training and certification resources.

For outdoor wireless networks, especially in open areas prone to harsh weather, it’s crucial to install lightning arrestors to protect against electrical surges caused by lightning strikes. Additionally, grounding the antenna cables helps dissipate any electrical charge that could damage the equipment.

 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.

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.

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 pre-deployment site survey, it’s important to know the AP model to understand the capabilities and coverage pattern of the APs. Additionally, knowing the number of clients helps to design a network that can handle the expected client density.

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

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

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 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.

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

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)

 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.

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.

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

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.

For Cisco Wireless LAN Controllers (WLCs) to operate in High Availability (HA) with Stateful Switch Over (SSO), they must be connected through a Redundancy Port (RP). This dedicated port is used for synchronization of stateful information and ensuring seamless failover without service interruption.

An SNR (Signal-to-Noise Ratio) less than 15 dB within the cell boundary during an AP-on-a-stick survey indicates that there is interference affecting the AP’s signal. This interference could be from another signal source that is reducing the quality of the connection, despite the signal strength being within the acceptable cell boundary of -67 dBm.

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.

 In a historic building where aesthetics are important, using APs with integrated antennas can minimize visual impact as they are often designed to be compact and less conspicuous. Patch antennas are also a good choice as they can be mounted flat against surfaces, blending in with the environment while providing directional coverage.

Creating a mobility group requires that all Wireless LAN Controllers (WLCs) share the same mobility group name. This allows them to recognize each other as peers and participate in client mobility events. The WLCs must be defined as peers in each other’s static mobility members list to facilitate inter-controller communication and roaming.

 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

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

 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 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.

 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)

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.

Setting the Anchor priority for the primary controller to 1 ensures that clients connect to the primary controller first. The Anchor priority is a value assigned to each controller within a mobility group to determine the order in which clients should connect to the controllers. A lower priority value has higher precedence. Therefore, by setting the primary controller’s Anchor priority to 1, it becomes the preferred controller for client connections. If the primary controller fails, clients are then pushed to the secondary controller, which should have a higher Anchor priority value.

 AP groups allow the engineer to apply different policies for APs in the auditorium versus those in the hallway. RRM (Radio Resource Management) can dynamically adjust the TX power and channel settings to optimize the wireless coverage and capacity.

 Large cases of liquid materials can cause higher signal loss compared to dry goods due to the way radio frequency (RF) waves interact with liquid, which can absorb and reflect the signals more than dry materials.

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.

References: The official Cisco ENWLSD 300-425 certification guide will have more details on conducting site surveys.

https://www.cisco.com/c/en/us/td/docs/wireless/technology/mesh/8-4/b_mesh_84/Site_Preparation_and_Planning.html#ID3405

 When performing a site survey of a large outdoor area, a site survey tool with a GPS module is ideal. The GPS module allows for precise location tracking, which is essential for mapping signal coverage over a large area. This tool can help complete the survey efficiently by automatically recording the location of signal measurements

 When designing a backhaul link, the mesh AP role should be set to ‘bridge’ to enable it to connect separate network segments or extend coverage to remote areas.

 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.

 For optimal Voice over WLAN (VoWLAN) design, a higher data rate is preferred to ensure quality of service and reliability. -67 dBm is a commonly recommended signal level for VoWLAN, and 802.11an, which operates in the 5 GHz band, is capable of supporting higher data rates compared to 802.11bgn, which operates in the 2.4 GHz band. The 5 GHz band is less crowded and prone to interference, making it suitable for high-speed data and voice applications.

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.

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.

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)

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.

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.