Free CWNP CWNA-109 Übungsprüfungen - Seite 22 von 34

Question #211

__________ antennas are designed to direct a signal in a specific direction.

A . Patch
B . Omnidirectional
C . Semidirectional
D . Planar

Question #212

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

Richtige Antwort: C
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

Question #213

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

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Question #214

What 802.11n mode of operation sends the same data on two adjacent 20 MHz channels?

A . Greenfield mode
B . HT Mixed mode
C . Non-HT duplicate mode
D . LDPC mode

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Question #215

Which of these encryption technologies have been cracked? (Choose all that apply.)

A . 64-bit WEP
B . TKIP/RC4
C . CCMP/AES
D . 128-bit WEP
E . Wired Equivalent Privacy

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Question #216

What mechanisms are specified by the IEEE 802.11 standard to attempt to prevent multiple radios from transmitting on the RF medium at a given point in time? (Choose 3)

A . Random backoff timer
B . Clear channel assessment
C . Network allocation vector
D . Slot assessment value
E . Collision detection

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Question #217

What are some of the security capabilities found in an enterprise WLAN router that is typically deployed in remote branch locations? (Choose all that apply.)

A . Integrated WIPS server
B . Integrated VPN server
C . Integrated NAC server
D . Integrated firewall
E . Integrated VPN client

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Question #218

A WLAN transmitter that emits a 200 mW signal is connected to a cable with 3 dB loss.

If the cable is connected to an antenna with 10 dBi gain, what is the EIRP at the antenna element?

A . 10 dBm
B . 13 dBm
C . 20 dBm
D . 26 dBm
E . 30 dBm

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Question #219

802.11ax BSS color information is communicated at both the PHY layer and the MAC sublayer.

Which of these statements are true about BSS color? (Choose all that apply.)

A . The primary BSS color identifiers are blue, red, and yellow.
B . The secondary BSS color identifiers are green, orange, and purple.
C . BSS color is a numerical identifier.
D . BSS color is an identifier of the basic service set.
E . BSS color is an identifier of the basic service area.

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Question #220

Which of the following is a better indicator of what outside influences are affecting an RF signal at a specific moment in time?

A . RSSI
B . SNR
C . EIRP
D . SINR

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