CWNA-109 Dumps with Practice Exam Questions Answers

 The frame type that is used to reserve the wireless medium for the transmission of high data rate frames that may not be understood by all clients connected to the BSS is RTS. RTS stands for Request to Send and is a control frame that is sent by a station to request access to the medium for a specified duration. The RTS frame contains the source and destination MAC addresses, as well as a Network Allocation Vector (NAV) value that indicates how long the medium will be occupied. The destination station responds with a Clear to Send (CTS) frame that echoes the NAV value and grants permission to the source station. All other stations in the BSS hear either the RTS or CTS frame and update their NAV timers accordingly, deferring their transmissions until the medium is free. The RTS/CTS mechanism can be used to prevent hidden node problems, reduce collisions, and protect high data rate frames that use features such as 802.11n or 802.11ac that may not be compatible with legacy stations. ACK, Beacon, and PS-Poll are not used to reserve the medium for high data rate frames. References: [CWNP Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 112; [CWNA: Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 102.

It is a channel that may require DFS when used is an important fact that should be considered about channel 128. Channel 128 is a 5 GHz frequency band 20 MHz channel that has a center frequency of 5.64 GHz. Channel 128 is one of the channels that are subject to DFS (Dynamic Frequency Selection) rules, which require Wi-Fi devices to monitor and avoid using channels that are occupied by radar systems or other primary users. DFS is a feature that is defined in the IEEE 802.11h amendment and is mandated by some regulatory bodies, such as the FCC and the ETSI, to protect the licensed users of the 5 GHz band from interference by unlicensed Wi-Fi devices. DFS works by using a mechanism called channel availability check (CAC), which requires Wi-Fi devices to scan a channel for a certain period of time before using it. If a radar signal is detected during the CAC or while using the channel, the Wi-Fi devices must switch to another channel that is free from radar interference.

When configuring an access point to use channel 128, it is important to consider the implications of DFS rules, such as:

• The access point must support DFS and comply with the local regulations and standards that apply to DFS channels.
• The access point may experience delays or interruptions in its operation due to CAC or channel switching.
• The access point may have limited channel selection or availability due to radar interference or other Wi-Fi devices using DFS channels.
• The access point may have compatibility or interoperability issues with some client devices that do not support DFS or use different DFS parameters.
• The access point may have performance or quality issues due to co-channel or adjacent-channel interference from other Wi-Fi devices using non-DFS channels.

Therefore, it is advisable to use channel 128 only when necessary and after performing a thorough site survey and spectrum analysis to determine the best channel for the access point. References: 1, Chapter 3, page 117; 2, Section 3.2

The solution that you recommend is an Overlay WLAN monitoring solution. An Overlay WLAN monitoring solution is a system that uses dedicated sensors or probes to monitor the WLAN performance over time. The sensors are deployed throughout the WLAN coverage area and collect data on various metrics such as signal strength, noise level, channel utilization, interference, throughput, latency, packet loss, and QoS. The sensors send the data to a centralized server or appliance that analyzes the data and provides a single pane of glass for administration and monitoring of the solution. An Overlay WLAN monitoring solution can help to detect and troubleshoot WLAN issues, optimize WLAN performance, and generate reports and alerts. References: [CWNP Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 538; [CWNA: Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 508.

The factors that will have the most significant impact on the amount of wireless bandwidth available to each station within a BSS are:

• The number of client stations associated to the BSS
• The presence of co-located (10m away) access points on non-overlapping channels

The number of client stations associated to the BSS affects the wireless bandwidth because each station shares the same channel and medium with other stations in the same BSS. The more stations there are, the more contention and collision there will be for the channel access, which reduces thethroughput and efficiency of the wireless communication. The wireless bandwidth available to each station depends on how the access point allocates the channel resources and how the stations use the channel time. For example, if the access point uses a round-robin scheduling algorithm, each station will get an equal share of the channel time regardless of its data rate or traffic demand. However, if the access point uses a proportional fair scheduling algorithm, each station will get a share of the channel time that is proportional to its data rate and traffic demand, which may result in higher or lower bandwidth for different stations.

The presence of co-located (10m away) access points on non-overlapping channels affects the wireless bandwidth because even though they use different channels, they may still cause interference and noise to each other due to channel leakage or imperfect filtering. The interference and noise can degrade the signal quality and SNR of the wireless communication, which reduces the data rate and throughput of the wireless communication. The wireless bandwidth available to each station depends on how well the access point and the station can cope with the interference and noise from other channels. For example, if the access point and the station support dynamic frequency selection (DFS) or adaptive radio management (ARM), they can switch to a less congested channel or adjust their output power or antenna gain to avoid or minimize interference from other channels.

References:1, Chapter 3, page 94;2, Section 3.2

In a public Wi-Fi hotspot, like the one Lynne runs in his hotel, ensuring customer security against active attacks is crucial. Active attacks involve unauthorized access, eavesdropping, or manipulation of the network traffic. To mitigate such threats, an effective and practical step is:

• Station-to-Station Traffic Blocking: Also known as client isolation, this feature prevents direct communication between devices connected to the Wi-Fi network. By enabling this on the access points, Lynne can significantly decrease the likelihood of active attacks like man-in-the-middle (MITM) attacks, where an attacker intercepts and possibly alters the communication between two parties.

The other options, while beneficial for network security, might not be as straightforward or practical for Lynne's situation:

• Network Access Control (NAC)requires a more complex infrastructure and management, which might not be ideal for a small hotel setup.
• Implementing an SSL VPNadds an extra layer of security but might complicate the login process for users, potentially affecting the user experience.
• Requiring EAP-FAST authenticationprovides secure authentication but may not be feasible for transient customers who expect quick and easy network access.

Therefore, enabling station-to-station traffic blocking is a practical and efficient measure that Lynne can implement to enhance customer security on the Wi-Fi network.

References:

• CWNA Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109, by David D. Coleman and David A. Westcott.
• Best practices for securing a wireless network in a public hotspot environment.