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Tenta December > Trådlösa Nätverk > Flashcards

Trådlösa Nätverk Flashcards

1
Q

Which two layers on the OSI-model does 802.11 operate?

A

1 and 2

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2
Q

True or False:

The Wi-Fi 5 certification is a certification program to ensure orderly and safe operation of a transceiver in the 5GHz frequency range

A

False

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3
Q

How can you represent an increase in power that is about equal to double the original value by using dB?

A

+3dB

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4
Q

What type of modulation does the picture show?

A

FSK

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5
Q

An 802.11b receiver is receiving signals from a transmitter. The radio waves have taken two diferent paths to the receiver, one straight ahead and one reflected due to multipath. The two waveforms arrive at the receiver 180° out of phase. What will happen to the received signal?

A

The waveforms will cancel eachother out (nulling)

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6
Q

Which propagation phenomena describes how a signal can bend or change direction as a result of passing through a medium of a different density?

A

Refraction

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7
Q

Wi-Fi Alliance recently introduced a new naming scheme. Which name is used by the Wi-Fi Alliance to refer to 802.11ac technology?

A

Wi-Fi 5

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8
Q

What is the frequency bandwidth for a single channel 802.11b DSSS transmission?

A

22 MHz wide

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9
Q

Which of these techniques divides a single 802.11 channel into 64 subcarriers, of which 52 are data subcarriers, that are then transmitted in parallel with each other?

A

OFDM

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10
Q

How many non-overlapping channels are there in the 2.4GHz ISM band?

A

3

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11
Q

Which are the non-overlapping channels in the 2.4GHz band that you should use in your channel reuse plan in most parts of the world?

A

Channel 1, 6 and 11

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12
Q

True or False:

All 5GHz channels are considered non-overlapping

A

True

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13
Q

True or False:

Channels 36 and 44 can be used together as a single 40MHz wide channel to increase data bandwidth. (channel bonding)

A

False

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14
Q

In some 5GHz U-NII bands DFS is a requirement. What is the purpose of DFS?

A

DFS is a radar avoidance technique

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15
Q

Which Wi-Fi certification program certifies functionality in the 6GHz frequency band?

A

Wi-Fi 6E

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16
Q

What is an example of a WWAN technique?

A

LTE (4G)

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17
Q

What is the most common distribution system medium (DSM) for a WLAN implementation?

A

Ethernet

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18
Q

The picture show a single dual-band 802.11n accesspoint, connected to a L3 switch, WLC and the Internet. The AP is broadcasting three SSIDs on both radios: “Students”, “Employees” and “Guest”

How would you best describe the picture?

A

The picture shows three basic service sets (BSS)

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19
Q

Which wireless architecture best describe the network in the picture?

A

Centralized architecture

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20
Q

How should the switchport connecting to the AP be configured?

A

As an access port

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21
Q

Where is the integration service located in this topology?

A

The WLC

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22
Q

If you were to open a WLAN discovery tool, how many unique BSSIDs would you find belonging to this AP in total?

A

6

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23
Q

What are some true statements about this picture?

A
  • The polar plot could be used to calculate the beamwidth of the antenna
  • The strongest signal radiating from the antenna is achieved at 90° and 270°
  • The picture shows the side view of an antenna (vertical)
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24
Q

In general, how does the gain of an antenna affect the vertical beamwidth of an omnidirectional antenna?

A

If the gain is increased, the vertical beamwidth gets more narrow

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25
Q

True or False:

Antenna polarization describes how the amplitude of the transmitted signal is oscillating from the antenna, for example horizontal or vertical polarization

A

True

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26
Q

True or False:

A dipole antenna is classified as a directional antenna

A

False

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27
Q

What is a yagi antenna clasified as?

A

Directional

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28
Q

Which protocol is used to connect a LAP and WLC?

A

CAPWAP

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29
Q

What needs to be true for a LAP and WLC to connect?

A
  • The LAP and WLC must have IP-connectivity to each other
  • The LAP needs to discover a controller IP-address before it can join
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30
Q

In the topology above we see two APs with one client each: Client A and Client B. All stations are within reach of one another with a signal strength of at least -65 dBm. Client A wants to send a frame to client B. Which alternative best describe how the trafic flow for the transmission would look like?

A

The frame is forwarded via AP-A to the switch, and then towards AP-B where it is then sent to Client B

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31
Q

How would you best describe firmware management for a Cisco lightweight AP?

A

The LAP will download image updates from the WLC if available

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32
Q

What medium access strategy is used in 802.11 to share the medium?

A

CSMA collision avoidance

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33
Q

What best describe the purpose of the Interframe space period?

A

The interframe space period allows certain frames to be prioritized, such as ACK-frames

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34
Q

What are not 802.11 frame types?

A
  • Security
  • Support
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35
Q

What is the purpose of a Block ACK frame?

A

A block ACK frame can acknowledge multiple frames at once

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36
Q

What technique can be implemented to prevent management frames from being spoofed?

A

Management frame protection (MFP)

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37
Q

The picture shows laptop AA:AA sending something to PC DD:DD on the wired network. If you were to look at the 802.11 frame during the transmission from laptop AA to the access point, what would the addressing of the frame look like in wireshark?

A
  • Reciver Address (RA): BB:BB
  • Transmitter Address (TA): AA:AA
  • Destination Address (DA): DD:DD
  • Source Address (SA): AA:AA
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38
Q

What does the do supplicant in 802.1x?

A

The supplicant is the host that requests authentication

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39
Q

Besides the supplicant, which other roles are defined in 802.1x?

A
  • Authentication server
  • Authenticator
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40
Q

Describe roaming:

A
  • Roaming is usually based on parameters such as RSSI, noise level and error rate
  • Roaming is initiated by the client station
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41
Q

What does WPA3 OWE do?

A

WPA3 OWE allows for encrypted data frames in an open network

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42
Q

What best describe the purpose of an Offline dictionary attack?

A

The purpose is to acquire a users password

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43
Q

What type of system can be deployed to monitor and protect the wireless network from attacks and threats?

A

A WIPS server

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44
Q

True or False:

With the hybrid site survey method, there is no need to physically visit a customer site

A

False

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45
Q

What is the purpose of attenuation spot checking in the hybrid site survey?

A

Determine attenuation values of different materials to be used in the predictive design

46
Q

What is not necessary to consider when performing a link budget calculation?

A

Cost

47
Q

Which technique allows a station to adjust the data rates used for transmission dynamically based on received signal quality?

A

DRS, Dynamic rate shifting

48
Q

What is a hidden node problem?

A

Two clients connected to the same BSS can hear the AP, but cannot hear each other

49
Q

What conclusions can we draw about the wireless network in the image above?

A

The design will result in a lot of adjacent-channel interference

50
Q

What is the purpose of capacity design when implementing a new network?

A

Capacity design ensures that we have enough radio capacity to provide for the users and their applications

51
Q

What can you do to improve performance in a high density environment?

A

Disable 802.11b

52
Q

What is the purpose of TPC in Cisco RRM?

A

TPC adjusts the transmit power of APs to reduce interference

53
Q

Which Cisco high-availability model is displayed in the picture?

A

N+N

54
Q

What is pre-802.11n antenna diversity?

A

A single radio equipped with multiple antennas could choose which one to use

55
Q

A user is upgrading from an old 802.11n smartphone without MIMO support, to a newer 802.11n 2x2:2 MIMO smartphone. In his apartment he has a 4x4:4 802.11n certified router. What can the user expect in regards to data rates used with his new device compared to the data rates he used to achieve?

A

The data rate will be doubled

56
Q

What protocol is the only protocol that does not use OFDM?

A

802.11b

57
Q

What spread spectrum technique does the protocol in 802.11b use instead of OFDM?

A

DSSS

58
Q

There are four 802.11 protocols that can be used for communication in the 2.4GHz band, which are they?

A
  • 802.11b
  • 802.11n
  • 802.11g
  • 802.11ax
59
Q

What is repeater mode in an AP?

A

Is used to extend the signal by retransmitting the signal to reach further.

60
Q

What is monitor mode in an AP?

A

An AP in monitor mode does not send/receive data, instead it listens to the transmissions going about around it to detect i.e., conflicting transmissions.

61
Q

What is the maximum data rate for 802.11ax?

A

9.687 Gbps

62
Q

What is the maximum data rate for 802.11g

A

54 Mbps

63
Q

What is the maximum data rate for 802.11b

A

11 Mbps

64
Q

What is the maximum data rate for 802.11a

A

54 Mbps

65
Q

What is the maximum data rate for 802.11n

A

600 Mbps

66
Q

What is the maximum data rate for 802.11ac

A

6.933 Gbps

67
Q

Which 802.11 protocols can be used for communication in the 5GHz band?

A
  • 802.11a
  • 802.11n
  • 802.11ac
  • 802.11ax
68
Q

Which protocol can be used for communication in the 6GHz band?

A

802.11ax

69
Q

Which organization can be seen as a global regulatory body and is tasked with global electromagnetic spectrum management?

A

ITU-R

70
Q

What type of modulation does this picture refer to?

A

Amplitude-shift keying (ASK)

71
Q

What type of modulation does the picture show?

A

Phase-shift keying (PSK)

72
Q

What is the relationship between frequency and wavelength?

A

If the frequency is increased, the wavelength gets decreased

73
Q

Which organization creates and publishes the different 802.11 standards used for wireless LAN communication?

A

IEEE

74
Q

What is the frequency bandwidth for a single channel 802.11ac transmission?

A

20MHz

75
Q

Which of these spectrum techniques was used in early legacy 802.11 wifi, and is used in some WPAN-standards today such as bluetooth?

A

FHSS

76
Q

What is the name of the 5GHz frequency bands that we are allowed to use in 802.11?

A

U-NII

77
Q

What is the first available 5GHz channel?

A

36

78
Q

True or False:

DFS is required for all outdoor 2.4GHz and 5GHz 802.11 implementations

A

False

79
Q

The wireless technology 802.16 WiMAX is an example of which wireless topology?

A

Wireless metropolitan area network (WMAN)

80
Q

Which connection state will a client station be in once they have fully connected to an access point and can send data?

A

Associated

81
Q

Which WLAN infrastructure term describes the layer 2 identifier of a basic service set?

A

BSSID

82
Q

What type of service set is shown in the picture?

A

An ESS

83
Q

What is roaming?

A

The process of a client transitioning from one AP to another while maintaining network connectivity

84
Q

What needs to happen for roaming to occur?

A
  • The coverage are (BSA) of two access points should overlap
  • The BSS should have the same SSID and security parameters
85
Q

Which service set is shown in the picture?

A

IBSS

86
Q

The typical dipole antenna has a gain of 1dBd. How many dBi is 1 dBd?

A

2.14+1=3.2

87
Q

What is the horizontal beamwidth of the typical dipole antenna? (Azimut/H-Plane)

A

360

88
Q

What components introduce a dB loss to the signal of a station?

A
  • Antenna cable
  • Connector
  • Attenuator
89
Q

What architecture use standalone APs without any WLAN controller or co-operation between access points?

A

Autonomous

90
Q

In general, which switch configuration line should be configured on the switchport connecting to a standalone AP?

A

if only 1 VLAN: Switchport mode access
if multiple VLAN: Switchport mode trunk

91
Q

Which two CAPWAP tunnels are built between a Cisco lighweight AP and WLC?

A

Control and Data

92
Q

DHCP option 43 is often used with Cisco LAPs. Which IP-adress should be given as the value of option 43?

A

The IP-address of the Cisco WLC

93
Q

What is carrier sense?

A

Carrier sense is performed by a transmitting station to determine if the medium is clear

94
Q

Which frame is sent by a receiving station if the CRC in the 802.11 trailer does not calculate correctly?

A

No frame is sent by the receiving station

95
Q

What does 802.11 management frame type do?

A

They are used by stations to join and leave the BSS

96
Q

Besides the management frame type, which other two 802.11 frame types exist?

A
  • Control
  • Data
97
Q

Which frames are part of the standard Wi-Fi association process?

A
  • Association request/response
  • Reassociation request/response
  • Disassociation
  • Probe request/response
  • Beacon
  • Authentication
  • Deauthentication
98
Q

What does the authenticator role do in 802.1x?

A

The authenticator allows or blocks traffic on a network port

99
Q

In a centralized wireless architecture with a WLC, where is the authenticator located?

A

The WLC

100
Q

What type of an attack is an Evil Twin attack?

A

Man-in-the-middle attack

101
Q

What type of security do you need to authenticate a wireless user through 802.1x and RADIUS?

A

WPA2 Enterprise

102
Q

What does a WIPS solution do?

A

A WIPS solution uses signature, behaviour, protocol and RF spectrum analysis to detect and prevent wireless threats

103
Q

What concept may be important when planning for outdoor bridge links, but not for indoor WLAN deployments?

A

Fresnel zone

104
Q

What is the asymmetric power problem?

A

An AP can hear the client, but the client cannot hear the AP

105
Q

With Wi-Fi 6E it is now possible to transmit in an additional frequency band other than the traditional 2.4GHz and 5GHz. What frequency band are you allowed to use with Wi-Fi 6E?

A

6GHz

106
Q

How many spatial streams does a 4x3:2 MIMO-AP support?

A

2

  • 4 Transmitted antennas
  • 3 number of receive antennas
  • 2 maximum spatial streams supported
107
Q

What is Multipath?

A

Multipath is a propagation phenomenon that results in two or more paths or copies of the same signal arriving at the antenna

108
Q

What is the purpose of frame check sequence (FCS) field in the 802.11 trailer of a data frame?

A

The FCS field contains a CRC, that is used to verify the integrity of the frame

109
Q

What is the purpose of the network allocation vector (NAV)?

A

The NAV timer is a form of logical carrier sense used to keep track of when the medium is busy

110
Q

Which frame

A

Tenta December (1 decks)

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