Exam Qs Flashcards
Which organization is the local regulatory body for Sweden and dictates how we can use the RF
spectrum for communication?
Swedish Post and Regulatory Body (PTS)
Which organization is responsible for creating the MAC and PHY specifications used in WLANs?
IEEE
Which dB value represent an approximate decrease in power equal to a tenth
(1/10) of the original value?
-10 dB
An administrator is increasing the transmit power of an AP from 10mW to 40mW. How much is
the power change in dB?
+6 dB
What does a frequency of 1 Hz mean for the waveform?
It means it completes 1 cycle per second
How many cycles are in 1 wavelength?
1
What best describes what phase is for an electromagnetic wave?
Phase is a relative term. It is the relationship between two waves with the same frequency
True or False: A 5GHz signal travels faster (in meters per second) than a 2.4GHz signal, often resulting in a
shorter WiFi range on 5GHz compared to 2.4GHz
False, the speed by which a signal travels depends on the medium through which it travels, not by its frequency
Describe what multipath is:
Multipath is a propagation phenomenon that results in two or more paths or copies of the same signal arriving at a receiving antenna.
The EIRP of a transmitting station is an important measurement of power that is often regulated.
Describe what the EIRP is.
The EIRP is the power a signal has just as it leaves the antenna. This means that the EIRP is the effective radiated power of a transmitter and antenna system in a specific direction
Which spectrum technique transmits on narrow channels across the entire frequency
band according to a predetermined hopping sequence?
Frequency Hopping Spread Spectrum (FHSS)
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?
1, 6, 11
All 802.11 communication in the 2.4GHz band use DSSS.
True or false?
False, can also be FHSS
All 802.11 communication in the 5GHz band use OFDM or OFDMA.
True or false?
True
Is all 802.11 communication half-duplex?
Yes, most 802.11 communication is half-duplex, which means that the devices can either send or receive data at a given time, but not both simultaneously. However, some 802.11 standards, such as 802.11n and 802.11ac, support a feature called multiple-input multiple-output (MIMO), which allows the devices to use multiple antennas to transmit and receive data simultaneously on different spatial streams, effectively achieving full-duplex communication
Describe how a wireless client communicates with a server on the
wired network?
The access point will strip the 802.11 frame and add an 802.3 frame header and trailer before sending it out the wired network.
Describe a WPAN?
A WPAN is typically used for communication between computer devices or peripherals.
In what context are WLANs usually used?
A WLAN typically provides networking for buildings such as homes or offices.
Which WLAN infrastructure term is used to describe the name configured by an administrator for
an 802.11 basic service set (BSS)?
SSID
Which WLAN infrastructure term is used to describe the coverage provided by a BSS?
BSA
Give an example of when an AP might have more than one BSSID.
An example of when an AP might have more than one BSSID is when the AP is configured to support multiple SSIDs.
Give an example of an omnidirectional antenna
A whip antenna is a type of antenna that consists of a straight flexible or rigid rod, often mounted on a portable radio device or a vehicle. A whip antenna radiates radio waves equally in all horizontal directions, and has a doughnut-shaped radiation pattern.
Give an example of a directional antenna.
(Use the correct name of the antenna type/style)
A Yagi antenna radiates radio waves in a narrow beam in the direction of the directors, and has a high gain and directivity. A Yagi antenna is usually a half-wave dipole antenna, which means that its length is approximately one half of the wavelength of the radio waves it transmits or receives
True or false: Polar plots display the radiation pattern of an antenna
True
True or false: Antenna polarization describes the impedance of the antenna
False
Besides the CAPWAP data tunnel, which other tunnel is built between a LAP and WLC?
CAPWAP control tunnel
If a client wants to send a message to another client on the same wireless network, does a WLC need to be involved in the transmission?
Yes, it can’t just go from the first client to the second via the LAP; the LAP does not forward traffic directly to the destination client
A switchport connected to the data port of a lightweight access point broadcasting two WLANs
should be configured with…
switchport mode trunk
Name two different ways or techniques that a lightweight access point can use to discover a
WLC address.
DHCP server discovery with option 43
DNS discovery:
During initial configuration of a 2504 WLC you are required to enter an address for the virtual
interface (virtual gateway IP). What is the interface used for?
The interface is used only for certain client facing operations, such as DHCP relay and
client mobility
When joining a WLC, an LAP of supported model can downlod both the correct firmware image
and config from the WLC.
True or false?
True. This is because the WLC provides all the configuration parameters and firmware that the LAP needs in the registration process.
What is the purpose of the frame check sequence (FCS) field in the 802.11 trailer of a data
frame?
The FCS field contains a CRC, that is used to verify the integrity of the frame
The 802.11e amendment introduced several improvements to the original CSMA/CA method. Name three:
Block ACK, frame bursts, QoS
Describe the purpose of the network allocation vector (NAV
timer)
The NAV timer is a form of logical carrier sense used to keep track of when the medium is
busy
What is the difference between RA address and DA address?
RA address is for example the AP the frame is heading towards, but the Destination is the MAC of the final destination
When would source address and transmitter address be different in the 802.11 frame?
The source address and the transmitter address would be different in the 802.11 frame when the frame is sent or received by an intermediate device, such as an access point or a mesh node, that is part of a distribution system or a wireless network. In this case, the source address is the MAC address of the original sender of the frame, and the transmitter address is the MAC address of the system that is directly transmitting the frame.
Which frame will a client station send when it is actively scanning for a network?
Probe request
Is it the access point or the client station that decides when the client should roam to a new AP?
The client station
What is an important factor in deciding if Rogue APs are harmful?
If they are on the wired network or not
True or false: With WPA2, unique encryption keys are generated dynamically for each user and each session
True
True or false: The static encryption key is shared among all stations in the WLAN.
True
True or false: A static encryption key is unique to a station, but always the same
False
What type of security is used when you authenticate users through a pre-shared key that is
configured on the AP?
WPA2 Personal
WPA3 has no backwards compatibility for older WPA2 clients. Thus, if WPA3 is to be used all
clients must support WPA3
True or false?
False, WPA3 has backwards compatibility
What is a captive portal?
A captive portal is a web-portal clients must interact with before they are allowed to use the
WLAN
What best describes the signal-noise ratio?
The difference between the received signal strength and the noise floor, a higher SNR is better
What occurs when two or more transmitters use overlapping channels?
Adjacent channel interference
Do overlapping channels cause co-channel interference?
No
What type of problem do you generally get when there is a lot of co-channel interference ?
High medium contention overhead
What device is suitable for detecting interference from non 802.11 sources during a site survey?
A spectrum analyzer
What describes a method to determine AP placements, where an initial site
visit is combined with a predictive design phase where virtual APs are placed on a blueprint to
predict RF-coverage?
Hybrid site survey
What best describes the purpose of DCA in Cisco RRM?
DCA adjusts the channel usage of APs to reduce interference
Which Cisco high-availability model uses a primary and backup wlc?
N+1
An 802.11n AP can be configured to use channels 36 and 40 together as a single 40MHz wide
channel to increase data bandwidth through channel bonding
True or false?
True
What is MU-MIMO?
An AP can transmit to several different clients at once by dividing the amount of available
spatial streams among the users
Which 802.11 protocol can reach a max data rate of 600 Mbps?
n
Which 802.11 protocol can reach a max data rate of 9.687
Gbps?
ax
Which 802.11 protocol can reach a max data rate of 6.933
Gbps?
ac
Which 802.11 protocols has a max data rate of 54 Mbps?
a and g
Which 802.11 protocol has a max data rate of 11 Mbps?
b
There are four 802.11 protocols that can be used for communication in the 2.4GHz band, which
are they?
b
ax
n
g
Which protocol is the only one to support communication in the 6GHz band?
ax aka Wi-Fi 6E
Explain what frequency bandwidth and data bandwith refers to for radio communication
Frequency bandwidth is typically measured in hertz (Hz) and indicates the range of frequencies that a signal occupies or a system can handle. Data bandwidth is the amount of data that can be transferred per unit of time over a communication channel. It is usually measured in bits per second (bps) and indicates the capacity or speed of a communication system.
Briefly explain the relationship between frequency bandwidth and the data bandwidth of a radio signal
In general, the higher the frequency bandwidth, the higher the data bandwidth, as more information can be encoded in a wider range of frequencies. However, there are also trade-offs between frequency bandwidth and data bandwidth, such as power consumption, interference, and complexity of the system.
Briefly explain the purpose of these two modes when talking about 802.11 FlexConnect mode, Sniffer mode
FlexConnect mode: This mode allows the LAP to locally switch traffic between an SSID and a VLAN if the CAPWAP tunnel to the wireless LAN controller (WLC) is offline. This mode is useful for remote locations where the WAN link to the WLC may be unreliable or have high latency. FlexConnect mode also supports features such as local authentication, local switching, and backup RADIUS servers1.
Sniffer mode: This mode enables the LAP to dedicate its radios to receiving 802.11 traffic from other devices, like a packet capture. The LAP then forwards all the packets on a particular channel to a remote machine that runs packet analyzer software, such as Wireshark or OmniPeek. This mode is useful for monitoring and troubleshooting 802.11 behavior, such as authentication, association, roaming, and encryption23.
Which of these organizations can be seen as a global regulatory body and is tasked with global
electromagnetic spectrum management?
ITU-R
An administrator is increasing the transmit power of an AP from 50mW to 100mW. How much did
the power change in dB?
3dB
1 decibel is equal to 1mW. True or false?
False, 1 decibel is a relative unit that describes the ratio between two values, such as signal-to-noise ratio. 1 milliwatt is an absolute unit of power.
An administrator is increasing the transmit power of an AP from 10mW to 200mW. How much is
the power change in dB?
+13dB
What does the term transceiver refer to?
A radio with receiver and transmitter functionality
What is a technique that changes the frequency of a carrier signal to encode binary data?
Frequency Shift Keying (FSK)
What is the relationship between frequency and wavelength?
If the frequency is increased, the wavelength gets decreased
What is diffraction?
Diffraction is the phenomenon of a radio wave bending around an obstacle or the edge of an object, such as a building, a hill, or a mountain. Diffraction occurs when the size of the obstacle is comparable to the wavelength of the wave.
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 90° out of phase. What will happen to the received signal?
The waveforms will cancel each other out (nulling). Nulling occurs when the reflected waves arrive exactly out of phase with the main signal and cancel each other out.
Which organization creates and publishes the different 802.11 standards used for wireless LAN
communication?
IEEE
Which spectrum technique was used in early legacy 802.11 wifi, and is used in some
WPAN-standards today such as bluetooth?
FHSS
What is the name of the 5GHz frequency bands that we in Europe are allowed to use in 802.11?
U-NII-1
U-NII-2
U-NII-3
The first available 5GHz channel is channel 36. True or false?
True
A single 6GHz Wi-Fi6E channel is 80MHz wide. True or false?
True
DFS is required for all outdoor 2.4GHz and 5GHz 802.11 implementations. True or false?
The answer is false. DFS is not required for all outdoor 2.4GHz and 5GHz 802.11 implementations, but only for those that operate in the same frequency range as radar systems
A 40 MHz channel has three times the data bandwidth compared to a 20 MHz channel. True or
false?
False, it has twice as much
The wireless technology 802.16 WiMAX is an example of which wireless topology?
Wireless metropolitan area network (WMAN)
Which connection state will a client station be in once they have fully connected to an access
point and can send data?
Associated
Which WLAN infrastructure term describes the layer 2 identifier of a basic service set?
BSSID
What does a BSS consist of?
A BSS usually consists of one access point and one or more client stations. The access point acts as a central hub that coordinates the transmission and reception of data packets among the client stations.
To allow for roaming, how should the APs be configured?
With the same SSID. To the user, all APs appear as a single unit. However, each AP will still have its own BSSID
What type of service set does not have an AP?
IBSS. This stands for Independent Basic Service Set, and it is a self-contained network that does not have an access point. An IBSS is also known as an ad hoc network
The typical dipole antenna has a gain of 1dBd. How many dBi is 1 dBd?
3.15 dBi
Name three components that introduce a dB loss to the signal of a station:
Antenna cable, connector, attenuator
The frequency an antenna is built for affects the physical size of the antenna. For instance, an
antenna built for 5GHz is generally of smaller size compared to an antenna of the same type built
for 2.4GHz.
True or false?
True. The frequency an antenna is built for affects the physical size of the antenna. The higher the frequency, the shorter the wavelength, and the smaller the antenna can be made.
What is true of the traffic flow when using a WLC?
All client traffic must pass through the WLC, except when the AP is configured for FlexConnect
Which architecture uses standalone APs without any WLAN controller or co-operation
between access points?
Autonomous
The switch configuration line that should be configured on the switchport connecting to one of these standalone APs is:
switchport mode trunk
A cisco LAP and WLC builds two tunnels:
Data tunnel and control tunnel
DHCP option 43 is often used with Cisco LAPs. Which IP-adress should be given as the value of
option 43?
The IP-address of the Cisco WLC
An LAP must be in the same VLAN and subnet as the WLC to be able to connect. True or false?
False
What best describes the purpose of carrier sense in CSMA/CA?
Carrier sense is performed by a transmitting station to determine if the medium is clear
Which frame is sent by a receiving station if the CRC in the 802.11 trailer does not calculate
correctly?
No frame is sent, if the CRC does not match the calculated value, the frame is discarded and no acknowledgment (ACK) frame is sent back to the sender. The sender will assume that the frame was lost or corrupted and will retransmit it after a timeout.
Name four aspects of CSMA/CA DCF:
IFS period
Carrier sense
NAV timer
Random backoff timer
Give an example of how 802.11 management frames are used?
They are used by stations to join and leave the BSS
Besides the management frame type, which other two 802.11 frame types exist?
Control
Data
Which frames are sent by the client or AP as part of the process of finding and
associating to a WLAN?
Probe Request
Association Request
Beacon Frame
What is the role of the authenticator?
The authenticator allows or blocks traffic on a network port
In a centralized wireless architecture with a WLC, where is the authenticator located?
WLC
What three things are necessary for a laptop to roam between two APs?
Same SSIDs, same channel and security settings. If they are on the same subnet it is also not necessary to get a new IP from a DHCP server
If a laptop roams between two APs on different subnets, in what context wouldn’t it need to get a new IP?
If the APs are working standalone without a WLAN-controller, so they do not perform any Layer 3 routing or switching.
An Evil twin attack is best described as what type of attack?
MITM
What type of security do you need to authenticate a wireless user through 802.1x and RADIUS?
WPA2 Enterprise
Describe a WIPS solution?
A WIPS solution uses signature, behaviour, protocol and RF spectrum analysis to detect and prevent wireless threats
Why is a Fresnel zone not relevant to indoor WLAN deployment?
Because a Fresnel zone is a region where there might be obstacles that deflect a wave, which outdoors means trees and hills. Indoors this is less relevant due to walls, floors, furniture etc
Describe the sniffer mode of a Cisco AP:
The LAP dedicates its radios to capturing 802.11 traffic from the air. The captured traffic can then be forwarded to a PC for further analysis.
What does it mean to have an asymmetric power problem?
For example that an AP can hear the client, but the client cannot hear the AP
Which would be the single most effective way to improve performance in a high density
environment?
Place more APs
Name three aspects of Cisco RRM? (Radio Resource Management)
DRS
TPC
DCA
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?
6GHz
How many spatial streams does a 4x3:2 MIMO-AP support?
2
What technique was introduced with 802.11ax and allows an AP to communicate with several
clients at once?
OFDMA
Which 802.11 protocol was the first to support MIMO spatial multiplexing?
n
There are two 802.11 protocols that can be used for communication in both the 2.4GHz band and
the 5GHz band. Which are they?
n
ax
How do you implement AP SSO?
You need to have two compatible WLCs with the same software version and license level. You also need to configure the redundancy management interface and the redundancy port on both WLCs and assign them to the same redundancy group
How does RTS/CTS work?
When a node wants to transmit data to another node, it sends out a RTS (Request to Send) frame. The receiver node replies with a CTS (Clear to Send) frame. The sender node waits for the CTS frame before sending the data frame. The receiver node sends an ACK (Acknowledgement) frame after receiving the data frame.
The first step of any site survey is to perform an Initial interview.
Name three topics that should be discussed with the customer during the initial interview.
Purpose of the survey
Existing network infrastructure
Budget
Briefly explain how a predicitve design process works. For instance, what input does the
software need and what is the result of the predictive design?
The software tool requires some input from the user, such as the floor plan of the site, the scale of the plan, the wall materials and thickness. The software tool then analyzes the input and generates a predictive design, which shows the optimal number, location, and configuration of the access points, as well as the expected coverage, performance, and capacity of the wireless network.
The Wi-Fi 5 certification is a certification program to ensure orderly and safe operation of a
transceiver in the 5GHz frequency range.
True or false?
False. The Wi-Fi 5 certification is a certification program by the Wi-Fi Alliance that indicates that a wireless device has met the industry standards for interoperability, security, and performance based on the IEEE 802.11ac protocol
Which term is used generally to describe an 802.11 radio capable unit?
Station
+x dB represents an approximate power change equal to twice the original power value. What is the value of x?
3
An administrator is decreasing the transmit power of an AP from 200mW to 20mW. How much did
the power change in dB?
The power change is equal to about minus 10 dB.
An administrator wants to increase AP1 to its maximum transmit power setting. This particular
model can be set from 0-30dBm. What will the resulting transmit power be in milliwatt if the setting of AP1 is changed from 14 dBm
to 30 dBm?
PmW = 10^(PdBm/10)
If we substitute 30 for PdBm, we get:
PmW = 10^(30/10) = 10^3 = 1000
Are sound waves examples of electromagnetic waves?
No
Electromagnetic waves travel at the speed of light. True or false?
True
Which propagation phenomena describes how a signal can bend or change direction as a result
of passing through a medium of a different density?
Refraction
Wi-Fi Alliance recently introduced a new naming scheme. Which name is used by the Wi-Fi
Alliance to refer to 802.11ac technology?
Wi-Fi 5
What is the frequency bandwidth for a single channel 802.11b DSSS transmission?
22MHz
Which technique divides a single 802.11 channel into 64 subcarriers, of which 52 are
data subcarriers, that are then transmitted in parallel with each other?
OFDM
How many non-overlapping channels are there in the 2.4GHz ISM band?
3 (the channels are 1, 6, 11)
All 5GHz channels are considered non-overlapping
True or false?
True
True or false:
Channels 36 and 44 can be used together as a single 40MHz wide channel to increase data
bandwidth. (channel bonding)
False
In some 5GHz U-NII bands DFS is a requirement. What is the purpose of DFS?
It is a radar avoidance technique
Which Wi-Fi certification program certifies functionality in the 6GHz frequency band?
Wi-Fi 6E
What is an example of a WWAN technique?
LTE (4G)
What is the most common distribution system medium (DSM) for a WLAN implementation?
Ethernet
Define ESS?
An extended service set (ESS) is a wireless network that consists of one or more basic service sets (BSSs) that are connected by a distribution system, such as Ethernet. A BSS is a group of wireless devices that share the same service set identifier (SSID) and communicate with a single access point (AP). An ESS allows wireless devices to roam seamlessly between different BSSs within the same network, as if they were in a single BSS.
Define centralised network architecture:
Multiple access points are connected to a central controller and a network switch
Where is the integration service in a centralised network architecture?
The integration service is located in the WLC in this topology. The integration service is a distribution system service that enables communication between stations that are associated with an access point and stations on a distribution system that are not 802.11 compliant, such as Ethernet devices.
If an AP is broadcasting 3 SSIDs on 2 radios, how many BSSIDs are there?
6
What is a polar plot?
A polar plot is a graphical representation of the radiation pattern of an antenna, which shows how the antenna radiates or receives electromagnetic waves in different directions.
How can you see if a polar plot shows a horizontal view?
Elevation is shown as 0 degrees, indicating the antenna points straight up
In general, how does the gain of an antenna affect the vertical beamwidth of an omnidirectional
antenna?
If the gain is increased, the vertical beamwidth gets more narrow
Antenna polarization describes how the amplitude of the transmitted signal is oscillating from the
antenna, for example horizontal or vertical polarization
True or false
True
A dipole antenna is classified as a directional antenna
True or false
The statement is false. A dipole antenna is classified as an omnidirectional antenna, not a directional antenna.
Is a yagi antenna a directional antenna?
Yes
Which protocol is used to connect a LAP and WLC?
CAPWAP
What are two factors are necessary for LAP and WLC to connect?
The LAP needs to discover a controller IP-address before it can join, and the LAP and WLC must have IP-connectivity to each other
Describe firmware management for a Cisco lightweight AP?
The LAP will download image updates from the WLC if available.
What medium access strategy is used in 802.11 to share the medium?
CSMA with collision avoidance
Describe the purpose of the interframe space period?
The interframe space period allows certain frames to be prioritized, such as ACK-frames.
What is the purpose of a Block ACK frame?
A block ACK frame can acknowledge multiple frames at once
What technique can be implemented to prevent management frames from being spoofed?
Management Frame Protection
Roaming is initiated by the client station, and roaming is usually based on parameters such as RSSI, noise level and error rate. True or false?
True
What does WPA3 OWE do?
It allows for encrypted frames on an open network
What is the purpose of an offline dictionary attack?
To get a user password
What type of system can be deployed to monitor and protect the wireless network from attacks
and threats?
WIPS
Name the traditional way to determine AP-placements during a site
survey, where a physical AP is tested and evaluated at different locations?
AP on a stick
Describe the purpose of attenuation spot checking in the hybrid site
survey?
Determine attenuation values of different materials to be used in the predictive design
Name 5 factors to include in a link budget calculation?
Frequency
Distance
Gains and losses
Transmit power
Free space path loss
The technique that allows a station to adjust the data rates used for transmission dynamically based on received signal quality is:
DRS, Dynamic rate shifting
What is a symptom of a hidden node problem?
Two clients connected to the same BSS can hear the AP, but cannot hear each other
This is because a hidden node problem occurs when a node can communicate with a wireless access point (AP), but cannot directly communicate with other nodes that are communicating with that AP
Is there overlap between channels 1, 4, 7, and 11?
Yes
The purpose of capacity design when implementing a new network is:
Capacity design ensures that we have enough radio capacity to provide for the users and their applications
The purpose of TPC in Cisco RRM is:
TPC adjusts the transmit power of APs to reduce interference
Describe pre-802.11n antenna diversity:
A single radio equipped with multiple antennas could choose which one to use
What does it mean for data rate if a new device supports 2x2:2 MIMO?
The new device can transmit and receive two spatial streams simultaneously, doubling the data rate compared to a single spatial stream device.
Describe OFDMA:
A client is assigned a subset of the OFDM subcarriers (RUs) in a channel to utilize for communication
Which is the only protocol that does not use OFDM?
b
It uses DSSS instead
