CWNP CWNA-109 Online Practice Questions and Exam Preparation

CWNP CWNA-109 Online Questions & Answers

• Question 51:

  When a STA has authenticated to an AP (AP-1), but still maintains a connection with another AP (AP-2), what is the state of the STA on AP-1?

  A. Transitional
  B. Unauthenticated and Unassociated
  C. Authenticated and Unassociated
  D. Authenticated and Associated
  C. Authenticated and Unassociated

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  Explanation/Reference:

  Authenticated and Unassociated. According to one of the web search results1, a STA can be authenticated to multiple APs, but it can only be associated to one AP at a time. Association is the process of establishing a logical link between the STA and the AP, which allows the STA to send and receive data frames through the AP2. Therefore, when a STA has authenticated to an AP-1, but still maintains a connection with another AP-2, it means that the STA is authenticated to both APs, but only associated to AP-2. The state of the STA on AP-1 is authenticated and unassociated, which means that the STA can switch to AP-1 without repeating the authentication process, but it cannot send or receive data frames through AP-1 until it becomes associated.

• Question 52:

  What can an impedance mismatch in the RF cables and connectors cause?

  A. Increased range of the RF signal
  B. Fewer MCS values in the MCS table
  C. Increased amplitude of the RF signal
  D. Excessive VSWR
  D. Excessive VSWR

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  Explanation/Reference:

  VSWR stands for Voltage Standing Wave Ratio, which is a measure of how well the impedance of the RF cable and connectors matches the impedance of the transmitter and the antenna. Impedance is the opposition to the flow of alternating current in an RF circuit, and it depends on the frequency, resistance, capacitance, and inductance of the components. A perfect impedance match would have a VSWR of 1:1, meaning that all the power is transferred from the transmitter to the antenna, and none is reflected back. However, in reality, there is always some degree of mismatch, which causes some power to be reflected back to the transmitter, creating standing waves along the cable. This reduces the efficiency and performance of the wireless system, and can also damage the transmitter. Excessive VSWR can be caused by using poor quality or damaged cables and connectors, or by using components that have different impedance ratings123. References: CWNA-109 Study Guide, Chapter 2: Radio Frequency Fundamentals, page 90; CWNA-109Study Guide, Chapter 2: Radio Frequency Fundamentals, page 86; CWNP website, CWNA Certification.

• Question 53:

  What primary metric of scanning can stations use to select the best AP for connectivity to the desired BSS?

  A. Signal strength of AP beacons received.
  B. PING latency when testing against an Internet server.
  C. Throughput speed in Mbps.
  D. FCS errors in frames transmitted to and from the AP.
  A. Signal strength of AP beacons received.

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  Explanation/Reference:

  When a station scans for available wireless networks, it listens for beacon frames sent by APs. A beacon frame contains information about the BSS, such as SSID, supported rates, channel, security, etc. The station also measures the signal strength of the beacon frames, which indicates how well the station can communicate with the AP. The signal strength is usually expressed in dBm or RSSI units. The higher the signal strength, the better the connection quality and performance. Therefore, the station can use the signal strength of AP beacons as the primary metric to select the best AP for connectivity to the desired BSS12. References: CWNA-109 Study Guide, Chapter 6: Wireless LAN Devices and Topologies, page 249; CWNA-109Study Guide, Chapter 6: Wireless LAN Devices and Topologies, page 243.

• Question 54:

  What is appended to the end of each 802.11 data frame after the payload?

  A. Preamble
  B. MAC header
  C. PHY header
  D. FCS
  D. FCS

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  Explanation/Reference:

  The FCS (Frame Check Sequence) is appended to the end of each 802.11 data frame after the payload. The FCS is a 4-byte field that contains a CRC-32 (Cyclic Redundancy Check) value that is calculated based on the contents of the MAC header and the payload of the frame. The FCS is used by the receiver to verify the integrity of the frame and to detect any errors or corruption that may have occurred during transmission. If the FCS does not match with the expected value, the frame is discarded by the receiver. References: , Chapter 4, page 139; , Section 4.2

• Question 55:

  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
  D. It has 4 radio chains

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  Explanation/Reference:

  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.

• Question 56:

  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?

  A. Use a 160 MHz channel on the 5 GHz radio
  B. Use a 40 MHz channel on the 5 GHz radio
  C. Install a second AP in the coverage area
  D. Use a 40 MHz channel on the 2.4 GHz radio
  B. Use a 40 MHz channel on the 5 GHz radio

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  Explanation/Reference:

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

• Question 57:

  What security solution is deprecated in the 802.11 standard and should never be used in any modern WLAN deployment?

  A. Shared Key Authentication
  B. Open System Authentication
  C. CCMP
  D. AES
  A. Shared Key Authentication

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  Explanation/Reference:

  Shared Key Authentication is a security solution that was defined in the original 802.11 standard as an alternative to Open System Authentication, which does not provide any security at all. Shared Key Authentication uses WEP (Wired Equivalent Privacy) to encrypt and authenticate data frames between the client station and the AP. However, WEP has been proven to be extremely vulnerable to various attacks that can easily crack the encryption key and compromise the network security. Therefore, Shared Key Authentication is deprecated in the 802.11 standard and should never be used in any modern WLAN deployment . References: [CWNA-109 Study Guide], Chapter 10: Wireless LAN Security, page 401; [CWNA-109Study Guide], Chapter 10: Wireless LAN Security, page 391; [Wikipedia], Wired Equivalent Privacy.

• Question 58:

  You are attempting to locate the cause of a performance problem in two WLAN cells in a mostly overlapping coverage area. You note that one AP is on channel 1 and the other is on channel 2. When you document your findings, what term do you use to describe the problem in this configuration?

  A. CCC
  B. Non-Wi-Fi interference
  C. CCI
  D. ACI
  C. CCI

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  Explanation/Reference:

  The term used to describe the problem in this configuration is Co-Channel Interference (CCI)1. CCI occurs when multiple access points are on the same or overlapping channels, causing interference and degradation in network performance1. In this case, one AP is on channel 1 and the other is on channel 2, which are overlapping channels, leading to CCI1.

• Question 59:

  You are implementing a VHT-capable AP. Which one of the following channels is available in the 802.11-2016 standard that was not available before the ratification of 802.11 ac?

  B. 161
  C. 153
  D. 144
  D. 144

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  Explanation/Reference:

  Channel 144 is a new channel that was added to the 5 GHz band by the 802.11ac amendment, which defines the VHT (Very High Throughput) PHY for WLANs. Channel 144 has a center frequency of 5720 MHz and a bandwidth of 20 MHz. It can also be combined with adjacent channels to form wider channels of 40 MHz, 80 MHz, or 160 MHz. Channel 144 is available in some regions, such as North America and Europe, but not in others, such as Japan and China . References: [CWNA-109 Study Guide], Chapter

  3: Antennas and Accessories, page 121; [CWNA-109Study Guide], Chapter 3: Antennas and Accessories, page 115; [Wikipedia], List of WLAN channels.

• Question 60:

  You are evaluating a connection that states the data rate is 150 Mbps. What is the expected throughput of this connection?

  A. Less than 150 Mbps because of 802.11 overhead and contention
  B. 54 Mbps because that is the actual maximum throughput of an 802.11 connection
  C. More than 150 Mbps because of compression
  D. 150 Mbps because the data rate is equal to the throughput
  A. Less than 150 Mbps because of 802.11 overhead and contention

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  Explanation/Reference:

  The data rate of a signal is the speed that the data bits in individual 802.11 data frames are sent, but it does not account for the actual amount of data that can be transmitted over time. The throughput of a connection is the flow of information over time, which is affected by various factors such as data encoding, modulation, encryption, airtime utilization, noise levels, interference, etc. Therefore, the throughput is always lower than the data rate. According to one of the web search results1, the actual throughput is normally 60-70 percent of the supported data rates. So, for a connection with a data rate of 150 Mbps, the expected throughput would be around 90-105 Mbps.