CWNP CWNA-109 Exam Practice Test Instant Access

Question 1

You have implemented an 802.11ax WLAN for a customer. All APs are four stream HE APs. The customer states that it is essential that most of the clients can use the OFDMA modulation scheme. What do you tell the customer?

AThe clients that must support OFDMA must also be upgraded to 802.11ax

BOFDMA is an optional feature of 802.11ax and most APs don't even support it

CAll 5 GHz PHYs use OFDM modulation, so you will achieve OFDMA everywhere in 5 GHz

DIf the devices support 802.11ac, they can be updated to support OFDMA through driver upgrades

Answer : A

OFDMA is a new modulation scheme introduced in 802.11ax that allows multiple users to share the same channel by dividing it into smaller subchannels called resource units (RUs). This improves the efficiency and capacity of the WLAN by reducing contention and overhead. However, to use OFDMA, both the AP and the client must support 802.11ax and negotiate the parameters of the subchannel allocation.Therefore, the customer needs to upgrade the clients that require OFDMA to 802.11ax devices12.

The other options are not correct because they do not reflect the reality of OFDMA.Option B is incorrect because OFDMA is a mandatory feature of 802.11ax for both downlink and uplink transmissions, and all 802.11ax APs must support it1. Option C is incorrect because OFDM and OFDMA are different modulation schemes, and OFDM does not allow multiple users to share the same channel.Option D is incorrect because 802.11ac devices cannot support OFDMA through driver upgrades, as they lack the hardware and firmware capabilities to do so2.

Question 2

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?

AThe sky was not as cloudy that day as it typically is and the sun also radiates electromagnetic waves.

BA new tenant in the building has set their AP to the same RF channel that your customer is using.

CThe antennas in the laptops have been repositioned.

DA few of your customer's users have Bluetooth enabled wireless headsets.

Answer : B

A possible cause of a sudden change in performance for the laptop computers is thata 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.Reference:[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.

Question 3

802. 11ax (HE) introduces Resource Units that can be used to allow communications with multiple devices at the same time, on the same channel, in the same BSS. What feature of 802.1 lax provides this functionality?

A6 GHz support

BTWT

CWi-Fi-LTE

DOFDMA

Answer : D

The feature of 802.11ax (HE) that provides this functionality isOFDM

A . OFDMA stands for Orthogonal Frequency Division Multiple Access and is a technology that allows multiple devices to communicate simultaneously on the same channel in the same BSS. OFDMA works by dividing a channel into smaller subchannels called Resource Units (RUs), which are composed of groups of subcarriers or tones. Each RU can be assigned to a different device based on its bandwidth requirement and signal quality. This way, OFDMA can increase the efficiency and capacity of the channel by reducing overhead, contention, and latency. OFDMA can also support both uplink and downlink multi-user transmissions using trigger frames and buffer status reports. 6 GHz support, TWT, and Wi-Fi-LTE are not features of 802.11ax that provide this functionality.Reference:[CWNP Certified Wireless Network Administrator Official Study Guide: Exam CWNA-109], page 226; [CWNA: Certified Wireless Network Administrator Official Study Guide: Exam CWNA-109], page 216.

Question 4

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?

AThe power budget in the edge switches must be carefully planned and monitored based on the number of supported PoE devices.

BThe edge Ethernet switches should support Ether-channel to get the best results out of the network.

CVoIP phones and 802.11 access points should not be powered by the same edge switch due to distortion.

DIf the switches are in optimal locations for VoIP phones, they are likely to be suboptimal locations for 802.11 APs

Answer : A

An immediate concern that you note after hearing this information is thatthe 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.Reference:[CWNP Certified Wireless Network Administrator Official Study Guide: Exam CWNA-109], page 234; [CWNA: Certified Wireless Network Administrator Official Study Guide: Exam CWNA-109], page 224.

Question 5

You support a WLAN using dual-band 802.11ac three stream access points. All access points have both the 2.4 GHz and 5 GHz radios enabled and use 40 MHz channels in 5 GHz and 20 MHz channels in 2.4 GHz. A manager is concerned about the fact that each access point is connected using a 1 Gbps Ethernet link. He is concerned that the Ethernet link will not be able to handle the load from the wireless radios. What do you tell him?

AHis concern is valid and the company should upgrade all Ethernet links to 10 Gbps immediately.

BHis concern is valid and the company should immediately plan to run a second 1 Gbps Ethernet link to each AP.

CHis concern is invalid because the AP will compress all data before transmitting it onto the Ethernet link.

DDue to 802.11 network operations and the dynamic rates used by devices on the network, the two radios will likely not exceed the 1 Gpbs Ethernet link.

Answer : D

What you should tell him is thatdue to 802.11 network operations and the dynamic rates used by devices on the network, the two radios will likely not exceed the 1 Gbps Ethernet link. This is because the actual throughput of an 802.11 network is much lower than the theoretical data rates due to factors such as overhead, contention, interference, retransmissions, and environmental conditions. Moreover, the data rates used by devices on the network vary depending on their distance, signal quality, capabilities, and configuration. Therefore, it is unlikely that both radios of the AP will simultaneously use the maximum data rates and saturate the 1 Gbps Ethernet link. Upgrading to a 10 Gbps Ethernet link or running a second 1 Gbps Ethernet link may be unnecessary and costly. Compressing all data before transmitting it onto the Ethernet link may introduce additional overhead and latency.Reference:[CWNP Certified Wireless Network Administrator Official Study Guide: Exam CWNA-109], page 227; [CWNA: Certified Wireless Network Administrator Official Study Guide: Exam CWNA-109], page 217.

Question 6

What 802.11 PHY uses available space in very low frequency ranges that is not in use at the time by broadcast video signals?

ADMG

BSIG

CDSSS

DTVHT

Answer : D

TVHT stands for Television Very High Throughput and it is a PHY defined by the 802.11af amendment. It uses the TV white space (TVWS) spectrum in the VHF and UHF bands between 54 and 790 MHz, which are not in use by broadcast video signals at the time. It can provide long-range and low-power connectivity for WLAN devices.

Question 7

You are evaluating access points for use in the 5 GHz frequency band. What PHY supports this band and supports 80 MHz channels?

AHT

BVHT

CERP

DOFDM

Answer : B

VHT stands for Very High Throughput, which is a physical layer (PHY) specification that supports the 5 GHz frequency band and supports 80 MHz channels. VHT is used by the IEEE 802.11ac standard, which is also known as Wi-Fi 5. VHT allows for higher data rates and more spatial streams than the previous HT (High Throughput) PHY, which is used by the IEEE 802.11n standard, also known as Wi-Fi 4.HT supports the 2.4 GHz and 5 GHz bands, but only supports up to 40 MHz channels12

The other options are not correct because:

ERP (option C) stands for Extended Rate PHY, which is a physical layer specification that supports the 2.4 GHz frequency band and supports up to 20 MHz channels. ERP is used by the IEEE 802.11g standard, which is also known as Wi-Fi 3.ERP allows for higher data rates than the previous DSSS (Direct Sequence Spread Spectrum) PHY, which is used by the IEEE 802.11b standard, also known as Wi-Fi 234

OFDM (option D) stands for Orthogonal Frequency Division Multiplexing, which is a modulation technique that divides a signal into multiple subcarriers that are spaced orthogonally to each other. OFDM is not a physical layer specification, but a common feature of many PHY specifications, including ERP, HT, and VHT.OFDM allows for higher spectral efficiency and robustness against multipath interference than the previous CCK (Complementary Code Keying) modulation technique used by DSSS34

CWNP CWNA-109 Certified Wireless Network Administrator Exam Practice Test