300-425 Questions and Answers

 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.

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.

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.

 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)

 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

The mesh backhaul link uses Advanced Encryption Standard (AES) for encryption. AES is a robust encryption standard that is widely used in various security protocols, including WPA2 and WPA3, to provide a high level of security for wireless communications. It ensures that the data transmitted over the mesh backhaul link is protected against unauthorized access and eavesdropping.

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

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 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.

 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.

 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.

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 Cisco 8540 Wireless Controller is designed for large enterprise and high-density environments. It has the capacity to manage up to 6000 access points, making it suitable for a multicampus architecture that needs to accommodate 4500 access points. Its high availability features ensure that all access points can be supported on one controller setup with minimal downtime.

 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.

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 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?

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.

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

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

 Interface groups allow for flexible WLAN to VLAN mappings by grouping multiple interfaces into a single entity. This enables a single WLAN to be mapped to multiple VLANs, providing scalability and flexibility in network design. AP groups are used to manage the configuration of multiple APs collectively, allowing for consistent WLAN to VLAN mappings across different APs in separate facilities.

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

 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.

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 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.

Aggregated Probe Response Optimization should be enabled on the controller to optimize roaming, especially for environments with a high density of Apple OS devices. This feature reduces airtime consumption and overhead by aggregating probe responses, which can improve the roaming experience for the employees.

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 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.

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

 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.

 Cisco workgroup bridges typically support up to 8 wired clients. With 42 users, each having a computer and a VoIP phone, that’s a total of 84 devices. To connect all devices while keeping costs at a minimum, the company would need 6 APs (as 7 x 12 = 84), with each AP supporting 14 devices (7 computers and 7 VoIP phones).

So, each AP will have 25 clients. Minimum 4 APs are sufficient.

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.

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

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)

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

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.

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

: 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.

References: Look for information on ‘Band Select’ in the official Cisco ENWLSD 300-425 certification guide.

 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.

 The AP fallback feature is designed to allow access points to return to their primary controller after they have connected to a secondary controller due to a failure or connectivity issue with the primary. This setting ensures that once the primary controller is back online, the APs will recognize it and re-establish their connection as per the original network design. This feature is crucial for maintaining the intended controller hierarchy and ensuring seamless wireless network operation.

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.

 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.

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.

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.

To address the sticky client problem, setting an RSSI (Received Signal Strength Indicator) threshold can help. This configuration will prompt clients to roam to a better AP when their signal strength falls below the set threshold, thus enhancing the roaming experience and ensuring clients are connected to the AP with the strongest signal available.

 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.

 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.

References: The official Cisco ENWLSD 300-425 certification guide will provide more information on RF optimization strategies.

https://www.cisco.com/c/en/us/td/docs/wireless/controller/8-10/config-guide/b_cg810/configuring_ap_groups.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

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.

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.

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.

IEEE 802.11ac Wave 2 APs are backward compatible with 802.11a/n clients, allowing these devices to connect and communicate with the newer APs, albeit at their respective maximum supported speeds.

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