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CWNP CWNA-109 Exam
Certified Wireless Network Administrator (Page 9 )

Updated On: 1-Feb-2026
Page 5 of 26
PDF with 122 Questions

What facts are true regarding controllers and APs in a Split MAC architecture?

  1. An IP tunnel is established between the AP and controller for AP management and control functions.
  2. Using centralized data forwarding, APs never tag Ethernet frames with VLAN identifiers or 802.1p CoS.
  3. With 802.1X/EAP security, the AP acts as the supplicant and the controller acts as the authenticator.
  4. Management and data frame types must be processed locally by the AP, while control frame types must be sent to the controller.

Answer(s): A

Explanation:

The fact that is true regarding controllers and APs in a Split MAC architecture is that an IP tunnel is established between the AP and controller for AP management and control functions. A Split MAC architecture is a WLAN architecture where some of the MAC layer functions are performed by the APs (such as encryption, decryption, and frame acknowledgement) and some are performed by the controllers (such as authentication, association, roaming, and QoS). To communicate with each other, the APs and controllers establish an IP tunnel that carries the management and control frames between them. The IP tunnel can use protocols such as Lightweight Access Point Protocol (LWAPP) or Control And Provisioning of Wireless Access Points (CAPWAP).


Reference:

[CWNP Certified Wireless Network Administrator Official Study Guide: Exam CWNA-109], page 372; [CWNA: Certified Wireless Network Administrator Official Study Guide: Exam CWNA-109], page 362.



The BSA of an AP covers the area used by the sales and marketing department. Thirty-five stations operate in this space. The users indicate that they need more throughput and all stations are 5 GHz capable 802.11ac clients. The current AP configuration uses 20 MHz channels in both 2.4 GHz and 5 GHz.
What is the least expensive solution available for increasing throughput for these users without implementing configuration options that are not recommended?

  1. Use a 160 MHz channel on the 5 GHz radio
  2. Use a 40 MHz channel on the 5 GHz radio
  3. Install a second AP in the coverage area
  4. Use a 40 MHz channel on the 2.4 GHz radio

Answer(s): B

Explanation:

The least expensive solution available for increasing throughput for these users without implementing configuration options that are not recommended is to use a 40 MHz channel on the 5 GHz radio. This solution can double the channel bandwidth and increase the data rates for the 5 GHz capable 802.11ac clients. Using a 40 MHz channel on the 5 GHz radio is also less likely to cause co- channel interference or overlap with other channels than using a 40 MHz channel on the 2.4 GHz radio, which has only three non-overlapping channels. Using a 160 MHz channel on the 5 GHz radio may provide even higher throughput, but it may also consume too much of the available spectrum and cause more interference with other devices or networks. Installing a second AP in the coverage area may also improve the throughput, but it may require additional costs and configuration.


Reference:

[CWNP Certified Wireless Network Administrator Official Study Guide:
Exam CWNA-109], page 216; [CWNA: Certified Wireless Network Administrator Official Study Guide:
Exam CWNA-109], page 206.



What factors will have the most significant impact on the amount of wireless bandwidth available to each station within a BSS? (Choose 2)

  1. The number of clientstations associated to the BSS
  2. The power management settings in the access point's beacons
  3. The presence of co-located (10m away) access points on non-overlapping channels
  4. The layer 3 protocol used by each station to transmit data over the wireless link

Answer(s): A

Explanation:

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 the throughput 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.


Reference:

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



The IEEE 802.11-2012 standard requires VHT capable devices to be backward compatible with devices using which other 802.11 physical layer specifications (PHYs)?

  1. OFDM
  2. HR/DSSS
  3. ERP-PBCC
  4. DSSS-OFDM

Answer(s): A

Explanation:

OFDM (Orthogonal Frequency Division Multiplexing) is the physical layer specification (PHY) that VHT

capable devices must be backward compatible with according to the IEEE 802.11-2012 standard. VHT (Very High Throughput) is a PHY and MAC enhancement that is defined in the IEEE 802.11ac amendment and is also known as Wi-Fi 5. VHT operates only in the 5 GHz band and uses features such as wider channel bandwidths (up to 160 MHz), higher modulation schemes (up to 256-QAM), more spatial streams (up to eight), multi-user MIMO (MU-MIMO), beamforming, and VHT PHY and MAC enhancements. VHT can achieve data rates up to 6.9 Gbps. According to the IEEE 802.11-2012 standard, VHT capable devices must be backward compatible with devices using OFDM PHY, which is defined in the IEEE 802.11a amendment and is also used by IEEE 802.11g, IEEE 802.11n, and IEEE 802.11h amendments. OFDM operates in both the 2.4 GHz and 5 GHz bands and uses features such as subcarriers, symbols, guard intervals, and OFDM PHY and MAC enhancements. OFDM can achieve data rates up to 54 Mbps. Backward compatibility means that VHT capable devices can interoperate with OFDM devices on the same network by using common features and parameters that are supported by both PHYs. For example, VHT capable devices can use a channel bandwidth of 20 MHz, a modulation scheme of BPSK, QPSK, or 16-QAM, one spatial stream, no beamforming, and OFDM PHY and MAC headers when communicating with OFDM devices. Backward compatibility also means that VHT capable devices can fall back to OFDM mode when the signal quality or SNR is too low for VHT mode.


Reference:

1, Chapter 3, page 123; 2, Section 3.2



You are configuring an access point to use channel 128.
What important fact should be considered about this channel?

  1. It is a 2.4 GHz frequency band 40 MHz channel, so it should not be used
  2. It is a 22 MHz channel so it will overlap with the channels above and below it
  3. It is a channel that may require DFS when used
  4. It is a channel that is unsupported by all access points in all regulatory domains

Answer(s): C

Explanation:

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.


Reference:

1, Chapter 3, page 117; 2, Section 3.2



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