Introduction to Networking: Wireless
What is a man-in-the-middle attack on a wireless local area network (LAN)?
A situation in which a hacker uses an access point (AP) to effectively hijack mobile nodes (clients) by sending a stronger signal than the legitimate AP is sending.
What is a slot time in an 802.11 wireless local area network (LAN)?
A standard period of time on a wireless LAN in which interframe spaces are inserted.
How might a wireless local area network (LAN) administrator ensure compliance with security audits?
Document audit procedures in the security policy.
Which term describes the operation mode of a basic service set (BSS)?
Infrastructure mode.
What is a wireless local area network (LAN) service set?
It describes the basic components of a fully operational wireless LAN.
To prevent hacker access to passwords and IP addresses, why would you want to place wireless access points (AP) on switches instead of hubs?
Switches prevent the broadcast of packets to all network segments.
Access points (AP) must support what encryption techniques in order to comply with 802.11i security standards?
Temporal Key Integrity Protocol (TKIP), Advanced Encryption Standard (AES), and AES-CCMP (Counter-Mode/CBC-MAC Protocol).
How do you troubleshoot a hidden node?
Test for degraded data throughput at all client locations.
Which Open Systems Interconnection model (OSI) layer do wireless local area networks (LAN) operate?
The Data Link Layer.
What are the three main conditions that influence the range of a wireless local area network (LAN)?
Transmission power, antenna type and location, and environment.
How might you confirm the presence of a hidden node on the network?
Turn on the request to send/clear to send (RTS/CTS) protocol and watch for increased network data throughput.
When should you consider enabling request to send/clear to send (RTS/CTS) protocol on a wireless LAN?
When large frames experience high collision rates.
Which of the networks or products in the answers listed below use spread spectrum technologies?
Wireless local area networks (LAN), Bluetooth, and global positioning systems (GPS).
Which of the following IEEE 802.11 wireless local area network (LAN) standards specifies both spread spectrum RF and infrared transmission technologies?
802.11.
What test instrument is used to locate and measure interfering narrowband RF signals in an 802.11 wireless local area network (LAN), among other things?
A spectrum analyzer.
How would you use a laptop computer, tablet, or smartphone when performing a site survey for a wireless local area network (LAN)?
By checking for signal strength and coverage while roaming around the facility.
What security service in an enterprise wireless gateway enables the wireless network administrator to assign levels of service to a particular user?
Class of service (CoS).
You wish to build a wireless network that provides significantly better throughput than a single 802.11b access point (AP). Which of the following is an acceptable solution?
Co-locate 802.11 frequency hop spread spectrum (FHSS) and 802.11 direct sequence spread spectrum (DSSS) APs in the same area.
What unit of measurement is used to express the gain of an antenna?
Decibels isotropic (dBi).
What challenges do wireless Internet service providers have to overcome in order to provide "last mile data delivery" to customers?
Distance to access points, rooftop access, lightning, trees, mountains, tower access, and other physical obstacles to connectivity.
In what direction does an omnidirectional antenna radiate RF energy?
Equally in all directions around its axis.
Which one of the following conditions occurs when an access point receives a distant client's signal at a lower power level than that of a nearer client?
Near/Far.
Which wireless client devices require drivers to be installed on the client node?
Wireless client devices on printed circuit (PC) cards that are to be installed in peripheral component interconnect (PCI) or industry standard architecture (ISA) adapters.
What are some basic questions you should ask a customer before visiting the customer's facility to perform a site survey?
The anticipated number of users, security requirements, data throughput requirements, and budget.
How are interframe spaces used in an 802.11 wireless local area network (LAN)?
They are used to defer a station's access to the medium and provide various levels of priority.
Which statement best describes a network application for which a wireless workgroup bridge is the best suited?
When remote buildings house small groups of wired clients needing wireless access to the main network.
Which version of the 802.11 wireless local area network (LAN) standard was the first to use orthogonal frequency division multiplexing (OFDM)?
802.11a.
Operation as an 802.11ac device occurs only in the 5 GHz Unlicensed National Information Infrastructure (UNII) radio band, so how are 802.11ac devices able to maintain compatibility with earlier standards that operate in the 2.4 GHz industrial, scientific, and medical (ISM) radio bands?
802.11ac devices also operate in the 2.4 GHz ISM range.
What causes co-channel interference in a wireless local area network (LAN)?
An overlap in the signal ranges of access points (AP) or different wireless LANs operating on the same channels.
Which term describes a wireless system in which the access point (AP) removes the wireless local area network's (LAN) service set identifier (SSID) from the beacon frames?
Closed system.
Bluetooth is a short range wireless personal area network (WPAN) technology that is covered under which Institute of Electrical and Electronics Engineers (IEEE) standard?
IEEE 802.15.
Which type of interframe space provides the highest level of priority network function control over the medium for a short time period?
Short interframe space (SIFS).
What are some common methods used to configure and manage access points?
Telnet/ssh (secure shell), universal serial bus (USB), and a built-in Web server for browser access.
Which of the voltage standing wave ratios (VSWR) shown below is best for transferring RF energy between connections?
1.2:1.
The Federal Communications Commission (FCC) rules regarding power output for frequency-hopping spread spectrum (FHSS) state that a maximum output to the intentional radiator with 5 MHz of carrier frequency bandwidth must be which one of the following?
125 mW.
What is the Federal Communications Commission (FCC) regulation for the maximum equivalent isotropically radiated power (EIRP) from a point-to-multipoint (PtMP) wireless local area network (LAN) antenna?
4 watts (W).
What wireless local area network (LAN) device can be described as a half-duplex device with intelligence equivalent to that of a sophisticated Ethernet switch?
An access point.
As a wireless local area network (LAN) administrator, why will you rarely see the "authenticated" step on the access point?
Because clients pass the authentication stage and immediately proceed into the association stage.
How can filtering augment some of the security limitations of Wired Equivalent Privacy (WEP) in a wireless local area network (LAN)?
By defining parameters to which client stations must adhere in order to gain access to the LAN.
As a general rule, how does an increase in effective isotropic radiated power (EIRP) relate to the link budget range?
Each 6 dB increase in EIRP equates to a doubling of range.
What information should you gather during the wireless local area network (LAN) site survey in a convention center for an upcoming trade show?
Identify who will be installing access points (AP) in ceilings that could be 40 feet high.
What is a consideration when mounting a high-gain omnidirectional antenna indoors on the ceiling?
If the ceiling is too high, the coverage area might not reach the floor where the users are located.
What can be done to increase the coverage area of a wireless local area network (LAN)?
Increase the transmission power, replace the omnidirectional antenna with a parabolic antenna, and use the 2.4 GHz radio band instead of the 5 GHz radio band.
What technologies does the 802.11n wireless standard use to achieve data rates as high as 600 megabits per second (Mbps)?
Multiple input, multiple output (MIMO) technology and spatial division multiplexing (SDM).
The ratio of the chipping code to data bits for a direct sequence spread spectrum (DSSS) signal is called which of the following?
Processing gain.
Which one of the following RF behaviors is defined as "the bending of a wave as it passes through a medium of different density"?
Refraction.
Which component of frequency hopping spread spectrum (FHSS) system creates more overhead than any similar component in a direct sequence spread spectrum (DSSS) system?
The interframe spacing.
In a frequency-hopping spread spectrum (FHSS) system that uses 10 frequencies across a 12 MHz frequency band, what happens if narrowband interference occurs at only one of the 10 frequencies?
The spread spectrum signal remains intact. Instead of being lost, the data on the interfered frequency is retransmitted on one of the other nine frequencies.
What are some measures that can be taken to prevent high voltage standing wave ratios (VSWR) in transmitters and receivers?
Tighten connections between cables and connectors and use impedance-matched hardware throughout.
In a segmented wireless local area network (LAN) that has a different Internet protocol (IP) address for each segment, which solution allows mobile clients to maintain their connectivity when roaming into different segments?
To deploy all access points (AP) on a single virtual LAN (VLAN) using a flat IP subnet for all APs so that no change of IP address for roaming clients occurs and all traffic goes through a central controller.
What are some desired features of an access point (AP) used to perform wireless local area network (LAN) site surveys?
Variable output power and external antenna connectors.
What causes the hidden node problem in a wireless local area network (LAN)?
When a client (or node) can receive signals from an access point (AP), but an obstacle prevents the client from receiving signals from the other clients that are connected to the network.
What information about access points (AP) should you detail in a wireless local area network (LAN) site survey?
Where and how should you place or mount each AP for maximum effectiveness; AP channels; and AP output power.
Which service includes cameras, motion sensors, and smoke and/or carbon monoxide detectors?
motion sensors
What is the maximum range of Class 2 (2.5 mW) Bluetooth devices?
10 meters or 33 feet.
Given an access point with 100 mW of output power connected through a cable with 3 dB of loss to the antenna with a 10 dBi gain, what is the approximate Equivalent Isotropically Radiated Power (EIRP) level from the antenna in mW?
100 mW.
How wide is each of the three wireless local area network (LAN) Unlicensed National Information Infrastructure (UNII) bands?
100 mW.
Which is the largest 802.11 data frame that can traverse a wireless local area network (LAN) without fragmentation?
2,346 bytes.
Why have 900 MHz industrial, scientific, and medical (ISM) band wireless local area networks (LAN) lost favor in comparison to 2.4 GHz and 5 GHz frequency systems?
900 MHz devices are more expensive and provide slower data throughput.
What Power over Ethernet (PoE) device picks off the DC voltage that has been injected into the CAT 5e cable by the injector and makes it available to the equipment through the regular DC power jack?
A DC picker or tap.
Residential gateways have been around for quite some time, but what capability was added to connect to Institute of Electrical and Electronics Engineers (IEEE) 802.11b, 802.11g, 802.11n, and 802.11ac compliant devices?
A Dynamic Host Configuration Protocol (DHCP) server and client.
What is the typical coverage pattern of a semidirectional antenna?
A hemispherical or cylindrical pattern.
What is a half-duplex device that is only capable of Open Systems Interconnection (OSI) model Layer 2 connectivity?
A wireless bridge.
Ideally, what should your next step be after you complete the wireless local area network (LAN) site survey and provide the survey results in a report to the customer?
A wireless consulting firm should be given the site survey report so that it will then be able to provide effective information on equipment purchasing and security solutions.
An independent basic service set (IBSS) is also commonly referred to as which one of the following?
Ad hoc mode.
Which statement best describes protocol filtering that has been implemented in a wireless bridge?
Allowing or denying wireless traffic using Open Systems Interconnection (OSI) model Layer 4 ports to filter Layer 7 applications.
What is the width of direct sequence spread spectrum (DSSS) channels and how far apart are their center frequencies spaced?
22 MHz and 5 MHz.
How does spread spectrum technology reduce the probability of signal jamming?
By transmitting over a wide frequency spectrum.
For maximum security, you should base your wireless local area network (LAN) user authentication on which one of the following?
Device-independent schemes, such as user names and passwords.
Although there are many different implementations of spread spectrum technology, what are the only types specified by the FCC in the Codes of Federal Regulation (CFR), volume 47, part 15?
Direct Sequencing Spread Spectrum (DSSS) and Frequency Hopping Spread Spectrum (FHSS).
What specific problem does a wireless local area network (LAN) resolve for corporations and home users?
Excessive data cabling.
Bluetooth uses which spread spectrum technology?
Frequency-hopping spread spectrum (FHSS).
What is the purpose of the distributed coordination function (DCF) in an 802.11 wireless local area network?
It allows all clients on a wireless LAN to contend for access on the shared RF transmission medium using the carrier sense multiple access with collision avoidance (CSMA/CA) protocol.
Which statement describes a passive injector?
It places DC voltage onto a CAT-5e cable.
What happens when an Active Ethernet switch fails to sense a power over Ethernet (PoE) device on a port?
It switches off the DC voltage on that port.
Why is direct sequence spread spectrum (DSSS) the most widely known and the most used of the spread spectrum types?
Its ease of implementation and high data rates.
What type of connectivity is needed to connect two networks between buildings that are located across the street from each other?
Point-to-point.
Wireless local area networks (LAN) that use an 802.1x protocol control network access on what basis?
Port-based.
Which one of the following power management modes populates a traffic indication map (TIM) in a basic or extended service set?
Power save polling (PSP) mode.
You are designing a wireless network to which several functional workgroups are connected. You want to configure your enterprise wireless gateway to allow you to quickly assign identical network access rights to persons within the same workgroup. Which enterprise wireless gateway feature provides this capability?
Role-Based Access Control (RBAC).
What is the tradeoff between the fragmenting of packets into shorter fragments versus longer packet fragments?
Shorter packet fragments have lower probability of errors from interference than longer packet fragments, but shorter packet fragments require more error correction.
Why is spread spectrum technology used in applications such as Bluetooth wireless personal area networks (WPAN)?
Spread spectrum technology allows wireless networking within a very short range.
When connecting to a wireless local area network (LAN), what is the most important point about the service set identifier (SSID)?
That the clients and all access points must be configured with matching SSIDs.
Which organization regulates the use of wireless local area network (LAN) devices in the United States?
The Federal Communications Commission (FCC)
Why is the Fresnel Zone important to the integrity of the RF link or path?
The Fresnel Zone defines an area around the RF line-of-sight (LOS) that can introduce RF signal interference if blocked.
As a subscriber enters a hotspot area, what signals their mobile wireless device of an available Wi-Fi network?
The access point (AP) advertises to the wireless device to enable connection.
Why is shared key authentication considered a security risk in a wireless local area network (LAN)?
The access point transmits the challenge text in the clear and receives the same challenge text encrypted with the wired equivalent privacy (WEP) key.
How does a client locate a wireless local area network (LAN) when performing passive scanning?
The client listens for beacons until it hears a beacon listing the service set identifier (SSID) of the network it wishes to join.
Why is it suggested that all data collected as part of a site survey for a wireless local area network (LAN) be included in the survey report as an attachment, appendix, or separate set of documentation?
The data could be needed in the future.
Why should a wireless network administrator consider installing an enterprise wireless gateway in their network?
The enterprise wireless gateway enables the wireless network administrator to manage a large wireless network using only a few central devices instead of a very large number of access points.
Polarization is defined as which one of the following?
The orientation of the electric field emitted from an antenna in relation to the earth's plane.
What is Equivalent Isotropically Radiated Power (EIRP)?
The power actually radiated by the antenna element.
Which of the following statements is true concerning Bluetooth technology?
To 802.11 networks operating in the 2.4 industrial, scientific, and medical (ISM) radio bands, Bluetooth transmissions appear as all-band noise.
Why are wireless local area networks (LAN) usually deployed in an access capacity instead of as the network's core layer?
Wireless LANs are generally incapable of meeting the requirements of the network core layer, which needs to be very fast and stable, able to handle a tremendous amount of traffic with little difficulty, and must experience no down time.
What initialization vector (IV) do most weak implementations of the Wireless Equivalency Protocol (WEP) use?
24 bit.
What device would a wireless local area network (LAN) administrator install between the access point or bridge and the network in order to give indoor LAN users as much bandwidth as possible?
A bandwidth control unit (BCU).
What test should you perform during the site survey to enable the design engineer to understand and control what the user's experience will be on the wireless local area network (LAN)?
A data throughput test.
What type of wireless local area network (LAN) attack could cost an employee their job because network usage logs point directly to the employee whenever a hacker gains access to the employee's domain login information and causes havoc on the network?
A passive attack.
In which of the following applications might a wireless LAN be deployed in a distribution layer role?
As a building-to-building bridge used to link corporate network segments.
In what manner do radio waves propagate (move) away from the source (antenna)?
In a straight line in all directions at once.
What should you note in the wireless local area network (LAN) site survey if a semidirectional antenna is required for adequate coverage?
The antenna orientation along with the antenna's side and back lobes for coverage and security reasons.
Why has it become cost-effective for enterprise companies to integrate wireless local area network (LAN) segments into their networks?
The cost of wireless technology has decreased and the quality has increased.
What is the purpose of the 802.11 wireless local area network (LAN) superframe?
To allow fair coexistence between point coordination function (PCF)-mode and distributed coordination function (DCF)-mode clients on the network.
What does the "on with threshold" setting of the request to send/clear to send (RTS/CTS) protocol allow the wireless local area network (LAN) administrator to control?
To control which frames over a certain size are announced and cleared to send by the stations.
Which one of the following wireless standards utilizes the 5 GHz frequency band for its signal transmissions?
802.11n.
What does the Institute of Electrical and Electronics Engineers (IEEE) specify as the maximum allowable power output into the intentional radiator for 802.11a, 802.11n, and 802.11ac compliant devices operating on the lower Unlicensed National Information Infrastructure (UNII) radio band?
40 mW.
What antenna type is ideal for making a point-to-point (P2P) network connection between two office buildings that are across the street from one another?
A semidirectional antenna.
How does RF line-of-sight (LOS) differ from visual LOS?
RF LOS is accompanied by a Fresnel Zone, a series of concentric ellipsoid-shaped areas around the visual LOS path.
Which one of the following tasks is the best choice for troubleshooting the near/far problem?
Review the location of the stations (clients) on the network.
What are some requirements of a wireless local area network (LAN) in a hospital that make it an effective training ground for individuals who want to immerse themselves in wireless LAN technology?
Roaming across large distances, a limited number of users on an access point (AP) due to mandated security, and medical applications that are often connection-oriented between the client and server.
