Network - Wireless Practice Questions 2

BSS (Basic Service Set):

A WLAN using a single access point.

ESS (Extended Service Set):

A WLAN using two access points.

Q: What technology do WLANs use to determine when they gain access to the wireless media? A. CSMA/CA B. SPF C. DUAL D. RSTP

Answer option A is correct

Q: Drag the maximum speed from the bottom onto their matching wireless standards. Each speed might be associated with more than one standard. 802.11a 802.11b 802.11g 802.11n

54Mbps 11Mbps 54Mbps >100Mbps

Q: Which of the following is used by IEEE 802.11n to achieve high throughput through the use of multiple antennas for transmission and reception? A. MIMO B. LACP C. FHSS D. DSSS

Answer option A is correct.

Q: What standard developed by the Wi-Fi Alliance implements the requirements of IEEE 802.11i? A. MIC B. TKIP C. WPA2 D. WEP

Answer option C is correct. Lesson: Wireless LANs

Carrier sense multiple access collision avoidance (CSMA/CA)

Just as CSMA/CD is needed for half-duplex Ethernet connections, CSMA/CA is needed for WLAN connections because of their half-duplex operation. Similar to how an Ethernet device listens to an Ethernet segment to determine whether a frame exists on the segment, a WLAN device listens for a transmission on a wireless channel to determine whether it is safe to transmit. In addition, the collision-avoidance part of the CSMA/CA algorithm causes wireless devices to wait for a random backoff time before transmitting.

Multiple input multiple output (MIMO)

Multiple input multiple output (MIMO) MIMO uses multiple antennas for transmission and reception. These antennas do not interfere with one another, thanks to MIMO's use of spatial multiplexing, which encodes data based on the antenna from which the data will be transmitted. Both reliability and throughput can be increased with MIMO's simultaneous use of multiple antennas.

Wi-Fi Protected Access (WPA)

The Wi-Fi Alliance (a nonprofit organization formed to certify interoperability of wireless devices) developed its own security standard to address the weaknesses of Wired Equivalent Privacy (WEP). This new security standard was called Wi-Fi Protected Access (WPA) Version 1.

Unidirectional antenna

Unidirectional antenna Unidirectional antennas can focus their power in a specific direction, thus avoiding potential interference with other wireless devices and perhaps reaching greater distances than those possible with omnidirectional antennas. One application for unidirectional antennas is interconnecting two nearby buildings.

Basic service set (BSS)

WLANs that have just one AP are called BSS WLANs. BSS WLANs are said to run in infrastructure mode because wireless clients connect to an AP, which is typically connected to a wired network infrastructure. A BSS network is often used in residential and SOHO locations, where the signal strength provided by a single AP is sufficient to service all of the WLAN's wireless clients.

Wi-Fi Protected Access Version 2 (WPA2)

Wi-Fi Protected Access Version 2 (WPA2) Uses Counter Mode with Cipher Block Chaining Message Authentication Code Protocol (CCMP) for integrity checking and Advanced Encryption Standard (AES) for encryption. These algorithms enhance the security offered by WPA.

Wired Equivalent Privacy (WEP)

Wired Equivalent Privacy (WEP) A security standard for WLANs. With WEP, an AP is configured with a static WEP key. Wireless clients needing to associate with an AP are configured with an identical key (making this a preshared key [PSK] approach to security). The IEEE 802.11 standard specifies a 40-bit WEP key, which is considered to be a relatively weak security measure.

Wireless router

Wireless router Attaches to a wired network and provides access to that wired network for wirelessly attached clients, like a wireless AP. However, a wireless router is configured such that the wired interface that connects to the rest of the network (or to the Internet) is on a different IP network than the wireless clients. Typically, a wireless router performs NATing between these two IP address spaces.

Channel bonding

With channel bonding, two wireless bands can be logically bonded together, forming a band with twice the bandwidth of an individual band. Some literature refers to channel bonding as 40-MHz mode, which refers to the bonding of two adjacent 20-MHz bands into a 40-MHz band.

IBSS (Independent Basic Service Set):

A WLAN without any use of a wireless access point.

Decibel (dB)

A ratio of radiated power to a reference value. In the case of dBi, the reference value is the signal strength (that is, the power) radiated from an isotropic antenna, which represents a theoretical antenna that radiates an equal amount of power in all directions (in a spherical pattern). An isotropic antenna is considered to have gain of 0 dBi.

802.11ac multiple input

An IEEE wireless networking standard operating in the 5GHz range, with increased throughput compared to previous WiFi IEEE standards.

Q: What IEEE 802.11 variant supports a maximum speed of 54 Mbps and uses the 2.4-GHz band? A. 802.11n B. 802.11g C. 802.11b D. 802.11a

Answer option B is correct

Q: WEP's RC4 approach to encryption uses a 24-bit string of characters added to transmitted data, such that the same plain-text data frame will never appear as the same WEP-encrypted data frame. What is this string of characters called? A. Chips B. Initialization vector C. Session key D. Orthogonal descriptor

Answer option B is correct.

Q: When extending the range for a 2.4-GHz WLAN, you can use nonoverlapping channels for adjacent coverage cells. However, there should be some overlap in coverage between those cells (using nonoverlapping channels) to prevent a connection from dropping as a user roams from one coverage cell to another. What percentage of coverage overlap is recommended for these adjacent cells? A. 5 percent to 10 percent B. 10 percent to 15 percent C. 15 percent to 20 percent D. 20 percent to 25 percent

Answer option B is correct.

Q: If a WLAN does not require a user to provide credentials to associate with a wireless AP and access the WLAN, what type of authentication is said to be in use? A. WEP B. SSID C. Open D. IV

Answer option C is correct.

Q: What type of antenna, commonly used in wireless APs and wireless routers in SOHO locations, radiates relatively equal power in all directions? A. Yagi B. Unidirectional C. Omnidirectional D. Parabolic

Answer option C is correct.

Q: A WLAN formed directly between wireless clients (without the use of a wireless AP) is referred to as what type of WLAN? A. Personal mode B. BSS C. Enterprise mode D. IBSS

Answer option D is correct.

Q: When using the 2.4-GHz band for multiple access points in a WLAN located in the United States, which nonoverlapping channels should you select? (Choose three.) A. 5 B. 6 C. 10 D. 11 E. 14 F. 0 G. 1

Answer options G, B, and D are correct.

Direct-sequence spread spectrum (DSSS)

Direct-sequence spread spectrum (DSSS) Modulates data over an entire range of frequencies using a series of symbols called chips. A chip is shorter in duration than a bit, meaning that chips are transmitted at a higher rate than the actual data. These chips not only represent encoded data to be transmitted, but also what appears to be random data. Because both parties involved in a DSSS communication know which chips represent actual data and which chips do not, if a third-party intercepted a DSSS transmission, it would be difficult for that party to eavesdrop on the data because he would not easily know which chips represented valid bits. DSSS is more subject to environmental factors, as opposed to FHSS and OFDM, because it uses an entire frequency spectrum.

Enterprise mode

Enterprise mode In the context of wireless networking, this refers to using a centralized authentication server such as RADIUS for authentication, instead of a pre-shared key (PSK).

Q: Jack works as a network administrator for Mac hill Inc. The company has a wireless local area network (WLAN). What will he do to prevent his wireless access point from being accessed by intruders? A. Implement SSL. B. Implement auditing. C. Implement WEP. D. Implement IPSec.

Explanation: Answer C is correct. To prevent his wireless access point from being accessed by intruders, Jack will implement Wired Equivalent Privacy (WEP) on the network. WEP secures the network using two components: authentication and encryption. WEP encrypts data on a wireless network by using a fixed secret key. Answer A is incorrect. Secure Sockets Layer (SSL) is an application layer protocol used to transmit private documents via the Internet. Answer B is incorrect. Auditing is used to track user accounts for file and object access, logon attempts, system shutdown, and so on. Answer D is incorrect. Internet Protocol Security (IPSec) is a standard-based protocol that provides the highest level of VPN security.

Q: You work as a technician for Mac.hill Inc. Rick, a sales manager, has a laptop that is compatible with 802.11b and 802.11g wireless networks. He complains that whenever he connects to his home network wirelessly, he gets the maximum connectivity speed of 11Mbps. However, when he connects his computer to the office wireless network, he gets much better connectivity speed. Which of the following steps will you take to resolve the issue? A. Replace his home network router with one that is 802.11g compatible. B. Replace his home network router with one that is 802.11b compatible. C. Replace his network card that supports only 802.11b network. D. Replace his network card that supports only 802.11g network.

Explanation: Answer option A is correct. According to the scenario, Rick's laptop is compatible with both 802.11b and 802.11g wireless networks. Furthermore, he doesn't get the connectivity speed better than 11Mbps at home network. The most likely cause of the issue is that his home wireless router is compatible to 802.11b standard only. In order to resolve the issue, change Rick's home router with one that is 802.11g compatible. Answer options D and C are incorrect because the scenario specifies that Rick is getting better speed at the office network. This indicates that the network card is working perfectly and does not require any replacement. Answer option B is incorrect because the wireless 802.11b standard provides the maximum transmission speed of 11Mbps.

Q: You need to implement wireless network on multiple floors of a large building and maintenance area. For this, you need to install access points (APs). What is your first concern before installing them? A. Channel overlap B. Encryption C. Authentication D. AP configuration

Explanation: Answer option A is correct. If you have a large area to cover with wireless, you need to be concerned with channel overlap.

Q: Which of the following wireless LAN (WLAN) security threats involves a user writing a symbol in a public place, letting other users know about the existence of a WLAN, and possibly information about how to access that WLAN? A. warchalking B. WEP and WPA security cracking C. rogue access point D. war driving

Explanation: Answer option A is correct. In the days when dial-up modems were popular, malicious users could run a program on their computer to call all phone numbers in a certain number range. Phone numbers that answered with modem tone then became potential targets for later attacks. This type of reconnaissance was known as "war dialing." A modern day variant of war dialing is "war driving," where malicious users drive around looking for unsecured WLANs. Once an open WLAN (or a WLAN whose SSID and authentication credentials are known) is found in a public place, a user might write a symbol on a wall (or some other nearby structure), letting others know the characteristics of the discovered network. This practice, which is a variant of the decades-old practice of hobos leaving symbols as messages to fellow hobos, is called "warchalking." Various security standards are available for encrypting WLAN traffic and authenticating a WLAN client with an AP. Two of the less secure standards include Wired Equivalent Privacy (WEP) and Wi-Fi Protected Access (WPA). While WPA is considered more secure than WEP, utilities are available on the Internet for cracking each of these approaches to wireless security. By collecting enough packets transmitted by a secure AP, these cracking utilities can use mathematical algorithms to determine the pre-shared key (PSK) configured on a wireless AP, with which an associating wireless client must also be configured. A malicious user could set up their own access point (AP) to which legitimate users could connect. Such an AP is called a rogue access point. That malicious user could then use a packet sniffer to eavesdrop on communication flowing through their access point. To cause unsuspecting users to connect to the rogue access point, the malicious user could configure the rogue access point with the same Service Set Identifier (SSID) used by a legitimate AP. When a rogue access point is configured with the SSID of a legitimate AP, the rogue access point is commonly referred to as an "evil twin."

Q: You work as a network administrator for Mac.hill Inc. You are configured a network. The network will include the provision for wireless access for the Sales Manager. Which of the following specifications defines the authentication method for wireless access? A. 802.1X B. 802.2 C. 802.3 D. 802.5

Explanation: Answer option A is correct. The 802.1X standard, defined by IEEE, is designed to enhance the security of wireless local area networks (WLANs) that follows the IEEE 802.11 standard. 802.1X provides an authentication framework for wireless LANs. It allows a user to be authenticated by a central authority. When a user requests access to an access point, the access point changes the user's status to an unauthorized state. It allows the client to send only an EAP start message. The access point returns an EAP message requesting for the user's identity. The client returns the identity, which is then forwarded by the access point to the authentication server. The authentication server uses an algorithm (multiple algorithms are possible) to authenticate the user and then returns accept or reject message to the access point. If the access point receives an accept message, it changes the user's status to the authorized state, which allows normal traffic to take place. In case of rejection, the client is disallowed to access the network. Answer option B is incorrect because 802.2 specification is commonly referred to as the LLC or Logical Link Control specification. Answer option C is incorrect because 802.3 specification defines the standards for Ethernet. It provides asynchronous networking using CSMA/CD (carrier sense, multiple access with collision detect) over coaxial, twisted-pair copper, and fiber media. Answer option D is incorrect because 802.5 specification defines a token-passing standard for twisted-pair, shielded copper cables.

Q: What is the maximum range of the IEEE 802.11n wireless standard? A. 70 m indoors/ 250 m outdoors B. 32 m indoors / 140 m outdoors C. 20 m indoors / 100 m outdoors D. 35 m indoors / 120 m outdoors

Explanation: Answer option A is correct. The maximum range of the IEEE 802.11n standard is 70 m indoors / 250 m outdoors. The maximum range of the original IEEE 802.11 standard is 20 m indoors / 100 m outdoors. The maximum range of the IEEE 802.11a standard is 35 m indoors / 120 outdoors. The maximum range of the IEEE 802.11b and IEEE 802.11g standards is 32 m indoors / 140 outdoors.

Q: You're concerned about war driving. You don't want to bring the hacker's attention to your wireless network. What will you do to mitigate this risk? A. Disable broadcast of SSID. B. Implement WEP. C. Implement WPA. D. Implement MAC filtering.

Explanation: Answer option A is correct. To mitigate the risk, you need to disable the broadcasting of SSID, as it will prevent war driving tools from detecting your network and improves network security. Answer options A and B are incorrect because encryption is an important step in preventing someone from hacking into your wireless network, but it will not prevent them from detecting it. So WPA and WEP encryptions are useless in this case. Answer option C is incorrect because MAC filtering can keep unauthorized computers from logging onto your network, but it will not make your network undetectable.

Q: You work as a technician for Mac.hill Inc. Rick, a sales manager, has a laptop that is compatible with 802.11b and 802.11g wireless networks. He complains that whenever he connects to his home network wirelessly, he gets the maximum connectivity speed of 11Mbps. However, when he connects his computer to the office wireless network, he gets much better connectivity speed. Which of the following steps will you take to resolve the issue? A. Replace his network card that supports only 802.11g network. B. Replace his home network router with one that is 802.11g compatible. C. Replace his home network router with one that is 802.11b compatible. D. Replace his network card that supports only 802.11b network.

Explanation: Answer option B is correct. According to the scenario, Rick's laptop is compatible with both 802.11b and 802.11g wireless networks. Furthermore, he doesn't get the connectivity speed better than 11Mbps at home network. The most likely cause of the issue is that his home wireless router is compatible to 802.11b standard only. In order to resolve the issue, change Rick's home router with one that is 802.11g compatible. Answer options A and D are incorrect because the scenario specifies that Rick is getting better speed at the office network. This indicates that the network card is working perfectly and does not require any replacement. Answer option C is incorrect because the wireless 802.11b standard provides the maximum transmission speed of 11Mbps.

Q: Adam has installed a wireless network in his home. Which of the following will help him to share his Internet connection to his surrounding neighbors? A. Install a directional antenna. B. Install an omnidirectional antenna. C. Install a router device. D. Install a bridge device.

Explanation: Answer option B is correct. Adam will install an omnidirectional antenna to share his Internet connection to his surrounding neighbors. An omnidirectional antenna radiates patterns or signals in all directions. This will provide his neighbors to access his wireless access point. Through WAP, they'll be able to access his Internet connection. Answer option A is incorrect because a directional antenna will radiate signals in a single direction. Answer options C and D are incorrect because a router and a bridge device will not help until they also act as WAP. As this is not specifically specified in the scenario hence these will not be the best choice.

Q: The IEEE 802.11b wireless standard has which of the following frequency band / maximum bandwidth parameters? A. 5 GHz / 54 Mbps B. 2.4 GHz / 11 Mbps C. 2.4 GHz / 54 Mbps D. 2.4 GHz or 5 GHz / > 300 Mbps

Explanation: Answer option B is correct. The 802.11b standard uses a frequency band of 2.4 GHz and has a maximum bandwidth of 11 Mbps. The 802.11a standard uses a frequency band of 5 GHz and has a maximum bandwidth of 54 Mbps. The 802.11g standard uses a frequency band of 2.4 GHz and has a maximum bandwidth of 54 Mbps. The 802.11n standard can operate using the 2.4 GHz frequency band or the 5 GHz frequency band, or both. The theoretical maximum bandwidth of 802.11n exceeds 300 Mbps.

Q: Which of the following wireless LAN (WLAN) security threats is also known as an "evil twin?" A. warchalking B. WEP and WPA security cracking C. rogue access point D. war driving

Explanation: Answer option C is correct. A malicious user could set up their own access point to which legitimate users would connect. Such an AP is called a rogue access point. That malicious user could then use a packet sniffer to eavesdrop on communication flowing through their access point. To cause unsuspecting users to connect to the rogue access point, the malicious user could configure the rogue access point with the same Service Set Identifier (SSID) used by a legitimate AP. When a rogue access point is configured with the SSID of legitimate AP, the rogue access point is commonly referred to as an "evil twin." Once an open WLAN (or a WLAN whose SSID and authentication credentials are known) is found in a public place, a user might write a symbol on a wall (or some other nearby structure), letting others know the characteristics of the discovered network. This practice, which is a variant of the decades-old practice of hobos leaving symbols as messages to fellow hobos, is called "warchalking." Various security standards are available for encrypting and authenticating a WLAN client with an AP. Two of the less secure standards include Wired Equivalent Privacy (WEP) and Wi-Fi Protected Access (WPA). While WPA is considered more secure than WEP, utilities are available on the Internet for cracking each of these approaches to wireless security. By collecting enough packets transmitted by a secure AP, these cracking utilities can use mathematical algorithms to determine the pre-shared key (PSK) configured on a wireless AP, with which an associating wireless client must also be configured. In the days when dial-up modems were popular, malicious users could run a program on their computer to call all phone numbers in a certain number range. Phone numbers that answered with modem tone then became potential targets for later attacks. This type of reconnaissance was known as "war dialing." A modern day variant of war dialing is "war driving," where malicious users drive around looking for unsecured WLANs.

Q: You need to implement wireless network on multiple floors of a large building and maintenance area. For this, you need to install access points (APs). What is your first concern before installing them? A. Authentication B. Encryption C. Channel overlap D. AP configuration

Explanation: Answer option C is correct. If you have a large area to cover with wireless, you need to be concerned with channel overlap.

Q: Which wireless LAN (WLAN) standards can operate in the 2.4 GHz frequency band? A. 802.11a B. 802.11b C. 802.11g D. 802.11n

Explanation: Answer options B, C, and D are correct. The 802.11a standard operates in the 5 GHz band. The 802.11b standard operates in the 2.4 GHz band. The 802.11g standard operates in the 2.4 GHz band. The 802.11n standard can operate in the 2.4 GHz or 5 GHz band (or both).

Q: Keith configured his wireless network with WEP encryption and has a limited number of users. He noticed that there are some unauthorized connections on his access point. Which of the following steps will he take to enhance the security of his network? Each correct answer represents a part of the solution. Choose two. A. Enable SSID broadcast. B. Configure WPA encryption. C. Configure MAC filtering. D. Change channel configuration.

Explanation: Answers B and C are correct. As a security measure, Keith will secure the wireless network by taking these steps: •Configure WPA encryption. •Configure MAC filtering. WPA encryption is stronger than WEP encryption. WEP encryption is the least secure encryption and is easy to break. By configuring MAC filtering, you will limit the number of devices that can connect to your wireless network. Answer A is incorrect because enabling SSID broadcast will make the network less secure. Answer D is incorrect because changing channel configuration will have no effect on wireless network security.

Q: Keith configured his wireless network with WEP encryption and has a limited number of users. He noticed that there are some unauthorized connections on his access point. Which of the following steps will he take to enhance the security of his network? Each correct answer represents a part of the solution. Choose two. A. Change channel configuration. B. Enable SSID broadcast. C. Configure WPA encryption. D. Configure MAC filtering.

Explanation: Answers C and D are correct. As a security measure, Keith will secure the wireless network by taking these steps: Configure WPA encryption. Configure MAC filtering. WPA encryption is stronger than WEP encryption. WEP encryption is the least secure encryption and is easy to break. By configuring MAC filtering, you will limit the number of devices that can connect to your wireless network. Answer B is incorrect because enabling SSID broadcast will make the network less secure. Answer A is incorrect because changing channel configuration will have no effect on wireless network security.

Extended service set (ESS)

Extended service set (ESS) WLANs containing more than one AP are called ESS WLANs. Like BSS WLANs, ESS WLANs operate in infrastructure mode. When you have more than one AP, take care to prevent one AP from interfering with another. Specifically, nonoverlapping channels (that is, channels 1, 6, and 11 for the 2.4-GHz band) should be selected for adjacent wireless coverage areas.

Frequency-hopping spread spectrum (FHSS)

Frequency-hopping spread spectrum (FHSS) Allows the participants in a communication to hop between predetermined frequencies. Security is enhanced because the participants can predict the next frequency to be used but a third party cannot easily predict the next frequency. FHSS can also provision extra bandwidth by simultaneously using more than one frequency.

War chalking

If an open WLAN (or a WLAN whose SSID and authentication credentials are known) is found in a public place, a user might write a symbol on a wall (or some other nearby structure) to let others know the characteristics of the discovered network. This practice, which is a variant of the decades-old practice of hobos leaving symbols as messages to fellow hobos, is called warchalking.

Independent basic service set (IBSS)

Independent basic service set (IBSS) A WLAN can be created without the use of an AP. Such a configuration, called an IBSS, is said to work in an ad-hoc fashion. An ad hoc WLAN is useful for temporary connections between wireless devices. For example, you might temporarily interconnect two laptop computers to transfer a few files.

Omnidirectional antenna

Omnidirectional antenna Radiates power at relatively equal power levels in all directions (somewhat similar to the theoretical isotropic antenna). Omnidirectional antennas are popular in residential WLANs and SOHO locations.

Orthogonal frequency-division multiplexing (OFDM)

Orthogonal frequency-division multiplexing (OFDM) Whereas DSSS uses a high modulation rate for the symbols it sends, OFDM uses a relatively slow modulation rate for symbols. This slower modulation rate, combined with the simultaneous transmission of data over 52 data streams, helps OFDM support high data rates while resisting crosstalk between the various data streams.

Personal mode

Personal mode In the context of wireless networking, this refers to using a pre-shared key (PSK) instead of a centralized server, such as RADIUS, for authentication.

802.11b

Ratified in 1999, this standard supports speeds as high as 11 Mbps. However, 5.5 Mbps is another supported data rate. The 802.11b standard uses the 2.4-GHz band and the DSSS transmission method.

802.11a

Ratified in 1999, this standard supports speeds as high as 54 Mbps. Other supported data rates (which can be used if conditions are not suitable for the 54-Mbps rate) include 6, 9, 12, 18, 24, 36, and 48 Mbps. The 802.11a standard uses the 5-GHz band and the OFDM transmission method.

802.11g

Ratified in 2003, this standard supports speeds as high as 54 Mbps. Like 802.11a, other supported data rates include 6, 9, 12, 18, 24, 36, and 48 Mbps. However, like 802.11b, 802.11g operates in the 2.4-GHz band, which allows it to offer backward compatibility to 802.11b devices. 802.11g can use either the OFDM or DSSS transmission method.

802.11n

Ratified in 2009, this standard supports a variety of speeds, depending on its implementation. Although the speed of an 802.11n network could approach 300 Mbps (through the use of channel bonding), many 802.11n devices on the market have speed ratings in the 130 to 150-Mbps range. Interestingly, an 802.11n WLAN can operate in the 2.4-GHz band, the 5-GHz band, or both simultaneously. 802.11n uses the OFDM transmission method.

Service set identifier (SSID)

Service set identifier (SSID) A string of characters that identifies a WLAN. APs participating in the same WLAN can be configured with identical SSIDs. An SSID shared among multiple APs is called an extended service set identifier (ESSID).

Wireless access point (AP)

Wireless access point (AP) A device that connects to a wired network and provides access to that wired network for clients that wirelessly attach to the AP.