CWNP CWNP Certifications CWNA-109 Questions & Answers

• Question 101:

  You administer a small WLAN with nine access point. As a small business, you do not rum a RADIUS server and use WPA2-Personal for security. Recently, you changed the passphrase for WPA2-personal in all Aps and clients. Several users are now reporting the inability to connect to the network at time and it is constrained to one area of the building. When using scanner, you see that the AP covering that area is online

  A. The AP that covers the problem area requires a firmware update

  B. The clients are improperly configured

  C. The AP that covers the problem area has failed

  D. The AP that covers the problem area is improperly configured

  Correct Answer: B

  This is because the passphrase for WPA2-Personal is case-sensitive and must match exactly on both the AP and the client. If the passphrase is entered incorrectly on the client, the client will not be able to authenticate with the AP and connect to the network. The AP that covers the problem area is not likely to require a firmware update, fail, or be improperly configured, as it is online and works with other clients that have the correct passphrase. To troubleshoot this issue, you can check the passphrase settings on the clients and make sure they matchwith the AP. You can also try to reconnect the clients to the network or reboot them if necessary. For more information on how to configure WPA2-Personal on your router

• Question 102:

  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)?

  A. OFDM

  B. HR/DSSS

  C. ERP-PBCC

  D. DSSS-OFDM

  Correct Answer: A

  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 aPHY 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 OFDMmode when the signal quality or SNR is too low for VHT mode. References: 1, Chapter 3, page 123; 2, Section 3.2

• Question 103:

  A natural disaster has occurred in a remote area that is approximately 57 miles from the response team headquarters. The response team must implement a local wireless network using 802.11 WLAN access points. What is the best method, of those listed, for implementation of a network back-haul for communications across the Internet in this scenario?

  A. 802.11 bridging to the response team headquarters

  B. Cellular/LTE/5G

  C. Turn up the output power of the WLAN at the response team headquarters

  D. Temporary wired DSL

  Correct Answer: B

  Cellular/LTE/5G is the best method for implementing a network backhaul for communications across the Internet in a remote area that is affected by a natural disaster. This is because cellular/LTE/5G networks are wireless and do not depend on physical infrastructure that may be damaged or unavailable in such scenarios. Cellular/LTE/5G networks also offer high-speed data transmission and wide coverage area, which are essential for emergency response operations. 802.11 bridging to the response team headquarters is not feasible because it requires line-of-sight and has limited range. Turning up the output power of the WLAN at the response team headquarters is not effective because it may cause interference and does not guarantee reliable connectivity. Temporary wired DSL is not practical because it requires installing cables and equipment that may not be available or accessible in a remote area. References: CWNA- 109 Study Guide, Chapter 7: Wireless LAN Topologies, page 2031

• Question 104:

  You must plan for POE in an office environment. Which one of these devices is least likely to be a POE PSE?

  A. Midspan multi-port injector

  B. Switch

  C. VolP Phone

  D. Midspan injector

  Correct Answer: C

  A VoIP phone is least likely to be a POE PSE of the devices listed. POE stands for Power over Ethernet, which is a technology that allows devices to receive both power and data over a single Ethernet cable. A POE PSE stands for Power Sourcing Equipment, which is a device that provides power to other devices over Ethernet. A POE PD stands for Powered Device, which is a device that receives power from a PSE over Ethernet. A midspan multi- port injector, a switch, and a midspan injector are examples of POE PSEs, as they can supply power to multiple devices over Ethernet cables. A VoIP phone is an example of a POE PD, as it can receive power from a PSE over an Ethernet cable. However, some VoIP phones can also act as POE PSEs for other devices, such as IP cameras or wireless access points, but this is not very common. References: CWNA-109 Study Guide, Chapter

  8: Wireless LAN Access Points, page 2411

• Question 105:

  Which IEEE 802.11 physical layer (PHY) specification includes support for operation in the 2.4 GHz, 5 GHz, and 6 GHz bands?

  A. VHT (802.11ac).

  B. HT(802.11n)

  C. HR/DSSS (802.11b)

  D. HE (802.11ax)

  Correct Answer: D

  The IEEE 802.11ax standard, also known as High-Efficiency Wireless (HEW) or simply HE, includes support for operation across multiple frequency bands: 2.4 GHz, 5 GHz, and, with the appropriate regulatory approvals, the 6 GHz band.

  This makes option D the correct answer. Here's how it compares to the other options:

  HE (802.11ax): Introduced as an enhancement over previous standards, 802.11ax is designed to improve efficiency, especially in dense environments. It supports operation in the 2.4 GHz, 5 GHz, and 6 GHz bands (the latter pending

  regulatory approval in various regions), making it highly versatile and future-proof. VHT (802.11ac): Very High Throughput, or 802.11ac, operates exclusively in the 5 GHz band. It introduced significant speed improvements over its

  predecessor (802.11n) but does not support the 2.4 GHz or 6 GHz bands. HT (802.11n): High Throughput, or 802.11n, supports operation in both the 2.4 GHz and 5 GHz bands. However, it does not include support for the 6 GHz band. HR/

  DSSS (802.11b): High-Rate Direct Sequence Spread Spectrum, or 802.11b, operates only in the 2.4 GHz band. It was one of the early Wi-Fi standards and does not support 5 GHz or 6 GHz bands.

  Given these distinctions, only 802.11ax (option D) supports operation across all three mentioned bands, aligning with the requirements stated in the question.

  References:

  IEEE 802.11ax-2021: High-Efficiency Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications.

  Understanding the 802.11ax (Wi-Fi 6) standard and its implications for modern wireless networking.

• Question 106:

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

  A. It is a 2.4 GHz frequency band 40 MHz channel, so it should not be used

  B. It is a 22 MHz channel so it will overlap with the channels above and below it

  C. It is a channel that may require DFS when used

  D. It is a channel that is unsupported by all access points in all regulatory domains

  Correct Answer: C

  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

• Question 107:

  What frame type 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?

  A. RTS

  B. ACK C. Beacon

  D. PS-Poll

  Correct Answer: A

  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.

• Question 108:

  What wireless networking term describes the increase of RF energy in an intentional direction with the use of an antenna?

  A. Directed Radiation

  B. Beam Digression

  C. Passive Gain

  D. Active Amplification

  Correct Answer: C

  Passive Gain is the increase of RF energy in an intentional direction with the use of an antenna. It is achieved by focusing the same amount of power into a smaller area, resulting in a higher power density and a stronger signal. Passive Gain does not require any additional power or amplification, but rather depends on the antenna's physical characteristics, such as size, shape, and orientation. Passive Gain is also expressed in decibels (dB) and is related to the antenna's beamwidth and directivity. References: 1, Chapter 2, page 63; 2, Section 2.3

• Question 109:

  A WLAN transmitter that emits a 50 mW signal is connected to a cable with 3 dB loss. If the cable is connected to an antenna with 9dBi gain, what is the EIRP at the antenna element?

  A. 26 dBm

  B. 13 dBm

  C. 23 dBm

  D. 10 dBm

  Correct Answer: C

  To calculate the EIRP at the antenna element, we need to add the transmitter output power, subtract the cable loss, and add the antenna gain. All these values need to be converted to dBm first, if they are not already given in that unit. In this case, we have: Transmitter output power = 50 mW = 10 log (50) dBm = 16.99 dBm Cable loss = 3 dB Antenna gain = 9 dBi EIRP = Transmitter output power - Cable loss + Antenna gain EIRP = 16.99 - 3 + 9 EIRP = 22.99 dBm Rounding up to the nearest integer, we get 23 dBm as the EIRP at the antenna element12. References: CWNA-109 Study Guide, Chapter 2: Radio Frequency Fundamentals, page 92; CWNA-109Study Guide, Chapter 2: Radio Frequency Fundamentals, page 88.

• Question 110:

  An AP is advertised as a tri-band, 4x4:4, Wi-Fi 6, 802. 11ax AP. Based on this information and assuming it is correctly advertised, what can be determined as certainly true about this AP?

  A. It supports four channels in 2.4 GHz and 4 channels in 5 GHz

  B. It supports UL-MU-MIMO

  C. It uses a modified OpenWRT firmware

  D. It has 4 radio chains

  Correct Answer: D

  Based on the information given, what can be determined as certainly true about this AP is that it has 4 radio chains. A radio chain is a hardware component that consists of an antenna, a radio frequency (RF) amplifier, and a transceiver. The

  number of radio chains indicates how many spatial streams an AP can transmit or receive simultaneously using Multiple Input Multiple Output (MIMO) technology. The notation x:y:z in an AP specification denotes the number of radio chains

  (x), the number of spatial streams (y), and the number of spatial streams per band (z). Therefore, a tri-band, 4x4:4, Wi-Fi 6, 802.11ax AP has four radio chains in each of its three bands (2.4 GHz, low 5 GHz, and high 5 GHz). It also supports

  four spatial streams in total and four spatial streams per band. It cannot be determined as certainly true that it supports four channels in each band, UL-MU-MIMO, or uses a modified OpenWRT firmware based on the information given.

  References: [CWNP Certified Wireless Network Administrator Official Study Guide:

  ExamCWNA-109], page 223; [CWNA: Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 213.