Free CWNP (CWNA-109) Certification Sample Questions with Online Practice Test
CWNA-109 Certification Study Guide Pass CWNA-109 Fast
NEW QUESTION # 25
Return Loss is the decrease of forward energy in a system when some of the power is being reflected back toward the transmitter. What will cause high return loss in an RF transmission system, including the radio, cables, connectors and antenna?
- A. A significant impedance mismatch between components in the RF system
- B. A Voltage Standing Wave Ratio (VSWR) of 1:1
- C. High output power at the transmitter and use of a low-gain antenna
- D. The use of 50 ohm cables longer than one meter in the RF system
Answer: A
Explanation:
Return loss is a measure of how well the components of an RF system are matched in terms of their impedance. Impedance is the opposition to the flow of alternating current in a circuit, and it depends on the frequency, resistance, capacitance, and inductance of the components. When the impedance of the source, the transmission line, and the load are not equal, some of the power is reflected back to the source, causing a loss of forward power. This loss is expressed in decibels (dB) as return loss. The higher the return loss, the lower the reflection and the better the impedance matching. Conversely, the lower the return loss, the higher the reflection and the worse the impedance matching.
VSWR (Voltage Standing Wave Ratio) is another way of expressing the same concept. It is the ratio of the maximum voltage to the minimum voltage along a transmission line due to the interference of the incident and reflected waves. A VSWR of 1:1 means that there is no reflection and perfect impedance matching. A VSWR higher than 1:1 means that there is some reflection and impedance mismatch. The higher the VSWR, the higher the reflection and the lower the return loss.
Therefore, a significant impedance mismatch between components in an RF system will cause high reflection, high VSWR, and low return loss.
NEW QUESTION # 26
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. CCI
- B. ACI
- C. Non-Wi-Fi interference
- D. CCC
Answer: A
Explanation:
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.
NEW QUESTION # 27
You are a small business wireless network consultant and provide WLAN services for various companies.
You receive a call from one of your customers stating that their laptop computers suddenly started experiencing much slower data transfers while connected to the WLAN. This company is located in a multi- tenant office building and the WLAN was designed to support laptops, tablets and mobile phones. What could cause a sudden change in performance for the laptop computers?
- A. A few of your customer's users have Bluetooth enabled wireless headsets.
- B. A new tenant in the building has set their AP to the same RF channel that your customer is using.
- C. The sky was not as cloudy that day as it typically is and the sun also radiates electromagnetic waves.
- D. The antennas in the laptops have been repositioned.
Answer: B
Explanation:
A possible cause of a sudden change in performance for the laptop computers is that a new tenant in the building has set their AP to the same RF channel that your customer is using. This can create co-channel interference (CCI), which is a situation where two or more APs or devices use the same or overlapping channels in the same area. CCI can degrade the performance of WLANs by increasing contention, collisions, retransmissions, and latency. CCI can also reduce the effective range and throughput of WLANs by lowering the signal-to-noise ratio (SNR). To avoid or mitigate CCI, it is recommended to use non-overlapping channels, adjust transmit power levels, or implement channel management techniques such as dynamic frequency selection (DFS) or load balancing. The sky condition, antenna position, or Bluetooth headset are not likely to cause a sudden change in performance for the laptop computers. References: [CWNP Certified Wireless Network Administrator Official Study Guide: Exam CWNA-109], page 81; [CWNA: Certified Wireless Network Administrator Official Study Guide: Exam CWNA-109], page 71.
NEW QUESTION # 28
When compared with legacy Power Save mode, how does VHT TXOP power save improve battery life for devices on a WLAN?
- A. VHT TXOP power save allows the WLAN transceiver to disable more components when in a low power state.
- B. VHT TXOP power save uses the partial AID in the preamble to allow clients to identify frames targeted for them.
- C. VHT TXOP power save allows stations to enter sleep mode and legacy Power Save does not.
- D. Legacy Power Save mode was removed in the 802.11ac amendment.
Answer: A
Explanation:
VHT TXOP (Very High Throughput Transmit Opportunity) power save is a feature introduced with the
802.11ac amendment, which is designed to improve the power efficiency of devices connected to a WLAN.
This feature enhances battery life in several ways, compared to the legacy Power Save mode:
* Enhanced Power Saving: VHT TXOP power save allows devices to disable more components of the WLAN transceiver when they are in a low power state. This reduces the power consumption during periods when the device is not actively transmitting or receiving data.
* Intelligent Wake-Up Mechanisms: It employs more sophisticated mechanisms for devices to determine when they need to wake up and listen to the channel, further reducing unnecessary power usage.
* Optimized Operation: This power save mode is optimized for the high-throughput environment of
802.11ac networks, allowing devices to efficiently manage power while maintaining high performance.
Legacy Power Save mode, introduced in earlier versions of the 802.11 standards, does not provide the same level of component disablement or the intelligent wake-up mechanisms found in VHT TXOP power save, making option B the correct answer.
References:
IEEE 802.11ac-2013 Amendment: Enhancements for Very High Throughput for Operation in Bands below 6 GHz.
CWNA Certified Wireless Network Administrator Official Study Guide: Exam CWNA-109, by David D.
Coleman and David A. Westcott.
NEW QUESTION # 29
You recently purchased four laptops containing dual-band 802.11ac adapters. The laptops can connect to your
2.4 GHz network, but they cannot connect to the 5 GHz network. The laptops do not show the 5 GHz SSIds, which are different than the 2.4 GHz SSIDs. Existing devices can connect to the 5 GHz SSIDs with no difficulty. What is the likely problem?
- A. Interference from non-Wi-Fi sources
- B. DoS attack
- C. Interference from other WLANs
- D. Faulty drivers
Answer: D
Explanation:
The likely problem that causes this scenario is faulty drivers. Drivers are software components that enable the communication between the operating system and the hardware devices, such as the wireless adapters. Faulty drivers can cause various issues with the wireless connectivity, such as not detecting or connecting to certain networks, dropping connections, or reducing performance. Faulty drivers can be caused by corrupted files, outdated versions, incompatible settings, or hardware defects. To fix faulty drivers, you can try to update, reinstall, or roll back the drivers, or contact the manufacturer for support. Interference from non-Wi-Fi sources, DoS attack, or interference from other WLANs are not likely to cause this scenario, as they would affect all devices in the same area, not just the new laptops. References: [CWNP Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 562; [CWNA: Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 532.
NEW QUESTION # 30
What is always required to establish a high quality 2.4 GHz RF link at a distance of 3 miles (5 kilometers)?
- A. Minimum output power level of 2 W
- B. A minimum antenna gain of 11 dBi at both endpoints
- C. Grid antennas ateach endpoint
- D. A Fresnel Zone that is at least 60% clear of obstructions
Answer: D
Explanation:
What is always required to establish a high quality 2.4 GHz RF link at a distance of 3 miles (5 kilometers) is a Fresnel Zone that is at least 60% clear of obstructions. The Fresnel Zone is an elliptical-shaped area around the line-of-sight path between two antennas that reflects and refracts the RF waves. The Fresnel Zone radius depends on the frequency of the RF signal and the distance between the antennas. For optimal performance, the Fresnel Zone should be at least 60% clear of any obstructions that may cause interference, attenuation, or multipath fading. The minimum output power level, antenna gain, and antenna type may vary depending on the environmental conditions and regulatory constraints, but they are not always required for a high quality RF link. References: [CWNP Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 75; [CWNA: Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page
65.
NEW QUESTION # 31
What statement about the IEEE 802.11-2016 QoS facility is true?
- A. 802.11 QoS is achieved by giving high priority queues a statistical advantage at winning contention.
- B. Four 802.1p user priorities are mapped to eight 802.11 transmit queues.
- C. When the Voice queue has frames awaiting transmission, no data will be transmitted from the Best Effort queue.
- D. 802.11 control frames are assigned to the 802.11 EF priority queue.
Answer: A
Explanation:
802.11 QoS is achieved by giving high priority queues a statistical advantage at winning contention. 802.11 QoS is based on the Enhanced Distributed Channel Access (EDCA) mechanism, which defines four access categories (ACs) for different types of traffic: Voice, Video, Best Effort, and Background. Each AC has its own transmit queue and contention parameters, such as Arbitration Interframe Space (AIFS), Contention Window (CW), and Transmission Opportunity (TXOP). These parameters determine how long a station has to wait before transmitting a frame and how long it can occupy the channel. Higher priority ACs have shorter AIFS, smaller CW, and longer TXOP, which means they have more chances to access the channel and send more data than lower priority ACs. However, this does not guarantee that higher priority ACs will always win the contention, as there is still a random backoff process involved. Therefore, 802.11 QoS is a statistical service that provides different levels of service quality based on traffic categories. References: , Chapter 10, page 403; , Section 6.1
NEW QUESTION # 32
When antenna gain is reported in dBi, the gain of the antenna is compared to what theoretical radiator?
- A. End-fire radiator
- B. Isotropic radiator
- C. Dipole radiator
- D. Anthropomorphic radiator
Answer: B
Explanation:
An isotropic radiator is a theoretical point source of electromagnetic radiation that radiates equally in all directions. It has no physical dimensions and no preferred direction of radiation. It is used as a reference for antenna gain because it represents the ideal case of a perfect omnidirectional antenna12 Antenna gain is a measure of how well an antenna concentrates its radiated power in a certain direction. It is expressed in decibels (dB) relative to a reference antenna. Whenthe reference antenna is an isotropic radiator, the antenna gain is denoted by dBi, which stands for decibels relative to isotropic12 For example, an antenna with a gain of 3 dBi means that it radiates 3 dB more power in its main direction than an isotropic radiator would. Conversely, an antenna with a gain of -3 dBi means that it radiates 3 dB less power in its main direction than an isotropic radiator would12
NEW QUESTION # 33
What statement about 802.11 WLAN bridges is true?
- A. WLAN bridges may support MIMO communications, but only if used in the 5 GHz frequency band
- B. WLAN bridges only work in the 2.4 GHz frequency band and they support only SISO communications
- C. WLAN bridges must use a channel with acceptable SNR at both transceivers to maintain the desired data rate bi-directionally
- D. WLAN bridges must be implemented such that no interference occurs on the channel anywhere between the two endpoints used to establish the bridge
Answer: C
Explanation:
WLAN bridges must use a channel with acceptable SNR at both transceivers to maintain the desired data rate bi-directionally. A WLAN bridge is a device that connects two or more networks using the 802.11 protocol. A WLAN bridge must have a clear and strong signal between the two endpoints to ensure reliable and fast data transmission. The signal-to-noise ratio (SNR) is a measure of the quality of the signal, which depends on the distance, interference, obstacles, and antenna gain between the transceivers. A higher SNR means a better signal quality and a higher data rate. A lower SNR means a worse signal quality and a lower data rate. Therefore, a WLAN bridge must use a channel with acceptable SNR at both transceivers to maintain the desired data rate bi-directionally1.
NEW QUESTION # 34
What cipher suite is specified by the 802.11-2016 standard and is not deprecated?
- A. Temporal Key Integrity Protocol
- B. Wired Equivalent Privacy
- C. Counter Mode with CBC-MAC Pro tocol
- D. Extensible Authentication Protocol
Answer: C
Explanation:
The cipher suite specified by the 802.11-2016 standard and is not deprecated is Counter Mode with CBC- MAC Protocol (CCMP). CCMP is an encryption protocol that uses Advanced Encryption Standard (AES) as the underlying cipher and provides confidentiality, integrity, and origin authentication for wireless data.
CCMP is the mandatory encryption protocol for WPA2 and WPA3. References: [CWNP Certified Wireless Network Administrator Official Study Guide: Exam CWNA-109], page 295; [IEEE Standard for Information technology-Telecommunications and information exchange between systems Local and metropolitan area networks-Specific requirements - Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications], page 1560.
NEW QUESTION # 35
In an 802.11n (H T) 2.4 GHz BSS, what prevents each station from using all the airtime when other client stations are actively communicating in the same BSS?
- A. OFDMA
- B. 802.11 DOS prevention
- C. CSMA/CD
- D. CSMA/CA
Answer: D
Explanation:
What prevents each station from using all the airtime when other client stations are actively communicating in the same BSS is CSMA/CA. CSMA/CA stands for Carrier Sense Multiple Access with Collision Avoidance and is a media access control method used by WLAN devices to share the wireless medium. CSMA/CA works by having each station sense the medium before transmitting a frame. If the medium is busy (i.e., another station is transmitting), the station defers its transmission until the medium is idle. If the medium is idle, the station waits for a random backoff period before transmitting. This way, CSMA/CA reduces the chances of collisions and ensures fair access to the medium for all stations. CSMA/CA also uses positive acknowledgements to confirm successful transmissions and retransmissions to recover from errors.
CSMA/CD, DOS prevention, and OFDMA are not used by WLAN devices in a BSS. References: [CWNP Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 108; [CWNA:
Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 98.
NEW QUESTION # 36
The requirements for a WLAN you are installing state that it must support unidirectional delays of less than
150 ms and the signal strength at all receivers can be no lower than -67 dBm. What application is likely used that demands these requirements?
- A. FTP
- B. VoIP
- C. E-Mail
- D. RTLS
Answer: B
Explanation:
VoIP (Voice over Internet Protocol) is an application that is likely used that demands the requirements of unidirectional delays of less than 150 ms and the signal strength at all receivers can be no lower than -67 dBm. VoIP is an application that allows users to make and receive voice calls over a network, such as the Internet or a WLAN. VoIP is a real-time and interactive application that requires high quality of service (QoS) to ensure good user experience and satisfaction. One of the QoS metrics for VoIP is delay, which is the time it takes for a voice packet to travel from the sender to the receiver. Delay can affect the quality and intelligibility of the voice conversation, as well as the synchronization and naturalness of the dialogue. The ITU-T G.114 recommendation suggests that the maximum acceptable one-way delay for VoIP should be less than 150 ms, as anything higher than that can cause noticeable degradation and annoyance to the users.
Another QoS metric for VoIP is signal strength, which is the measure of how strong the RF signal is at the receiver. Signal strength can affect the reliability and performance of the wireless connection, as well as the data rate and throughput of the VoIP traffic. The CWNA Official Study Guide recommends that the minimum signal strength for VoIP should be -67 dBm, as anything lower than that can cause packet loss, retries, jitter, and other issues that can impair the voice quality. References: 1, Chapter 10, page 398; 2, Section 6.1
NEW QUESTION # 37
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. DSSS-OFDM
- B. HR/DSSS
- C. ERP-PBCC
- D. OFDM
Answer: D
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 802.11 g, 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. References: 1, Chapter 3, page 123; 2, Section 3.2
NEW QUESTION # 38
You are installing an AP to be used by 27 laptops. All laptops will connect on the 5 GHz frequency band. A neighbor network uses channels 1 and 6. What channel should be used for this AP and why?
- A. Channel 1, because it is best to use the channel with the lowest frequency
- B. A 5 GHz channel, because channels 1 and 6 are 2.4 GHz channels they have no impact on the decision
- C. Channel 11, because channels 1 and 6 are in use nearby
- D. Channel 6, because it is always best to use this channel
Answer: B
Explanation:
A 5 GHz channel should be used for this AP because channels 1 and 6 are 2.4 GHz channels and they have no impact on the decision. The 5 GHz frequency band offers more non-overlapping channels than the 2.4 GHz frequency band, which reduces interference and improves performance. The 5 GHz frequency band also supports higher data rates and wider channel bandwidths than the 2.4 GHz frequency band, which increases capacity and throughput. The 5 GHz frequency band also has less interference from other devices and sources than the 2.4 GHz frequency band, which enhances reliability and quality of service. Therefore, it is recommended to use the 5 GHz frequency band for WLANs whenever possible. Channels 1 and 6 are two of the three non-overlapping channels in the 2.4 GHz frequency band (the other one is channel 11). They are used by a neighbor network in this scenario, but they do not affect the channel selection for this AP because they operate in a different frequency band than the 5 GHz frequency band. Channel 6 is not always best to use; it depends on the interference and congestion level in the environment. Channel 1 is not best to use because it has a lower frequency than channel 6; frequency does not determine channel quality or performance. Channel 11 is not best to use because it is also a 2.4 GHz channel and it may interfere with channels 1 and 6. References: CWNA-109 Study Guide, Chapter 4: Antenna Systems and Radio Frequency (RF) Components, page 113
NEW QUESTION # 39
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. Turn up the output power of the WLAN at the response team headquarters
- B. Temporary wired DSL
- C. 802.11 bridging to the response team headquarters
- D. Cellular/LTE/5G
Answer: D
Explanation:
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
NEW QUESTION # 40
A string of characters and digits is entered into an AP and a client STA for WPA2 security. The string is 8 characters long. What is this string called?
- A. Passphrase
- B. PSK
- C. MSK
- D. WEP key
Answer: A
Explanation:
The string of characters and digits that is entered into an AP and a client STA for WPA2 security and is 8 characters long is called a passphrase. A passphrase is a human-readable text that is used to generate a Pre-Shared Key (PSK) for WPA2-Personal security. A passphrase can be between 8 and 63 characters long and can include any ASCII character. The PSK is a 256-bit key that is derived from the passphrase using a hashing algorithm called PBKDF2. The PSK is used to encrypt and decrypt the data frames between the AP and the client STA. A MSK is a Master Session Key that is generated by an authentication server for WPA2-Enterprise security. A WEP key is a 40-bit or 104-bit key that is used for Wired Equivalent Privacy (WEP) security, which is deprecated and insecure. A PSK is not a string of characters and digits, but a binary key. References: [CWNP Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page 303; [CWNA: Certified Wireless Network Administrator Official Study Guide: ExamCWNA-109], page
293.
NEW QUESTION # 41
ABC Company is planning to install a new 802.11ac WLAN, but wants to upgrade its wired infrastructure first to provide the best user experience possible. ABC Company has hired you to perform the RF site survey.
During the interview with the network manager, you are told that the new Ethernet edge switches will support VoIP phones and 802.11 access points, both using 802.3 PoE.
After hearing this information, what immediate concerns do you note?
- A. The power budget in the edge switches must be carefully planned and monitored based on the number of supported PoE devices.
- B. The edge Ethernet switches should support Ether-channel to get the best results out of the network.
- C. VoIP phones and 802.11 access points should not be powered by the same edge switch due to distortion.
- D. If the switches are in optimal locations for VoIP phones, they are likely to be suboptimal locations for
802.11 APs
Answer: A
Explanation:
An immediate concern that you note after hearing this information is that the power budget in the edge switches must be carefully planned and monitored based on the number of supported PoE devices. PoE stands for Power over Ethernet and is a technology that allows Ethernet switches to deliver power along with data to devices such as VoIP phones and 802.11 access points. PoE devices are classified into different classes based on their power consumption and output. The edge switches have a limited power budget that determines how many PoE devices they can support simultaneously. If the power budget is exceeded, some PoE devices may not receive enough power or may shut down unexpectedly. Therefore,it is important to plan and monitor the power budget in the edge switches based on the number and class of PoE devices connected to them. Using Ether-channel, placing switches in optimal locations, or avoiding distortion are not immediate concerns related to PoE devices. References: [CWNP Certified Wireless Network Administrator Official Study Guide:
ExamCWNA-109], page 234; [CWNA: Certified Wireless Network Administrator Official Study Guide:
ExamCWNA-109], page 224.
NEW QUESTION # 42
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