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