CCNA FAQ: Understanding Wireless Networking

CCNA FAQ: Understanding Wireless Networking

Q1. Three agencies manage the standards and frequencies of wireless networks. List the names of these agencies and briefly describe their functions.

Answer: The agencies that govern wireless networks are as follows: The International Telecommunication Union-Radiocommunication Sector (ITU-R) regulates the radio frequencies used for wireless transmission. The Institute of Electrical and Electronic Engineers (IEEE) maintains the 802.11 wireless transmission standards. The Wi-Fi Alliance ensures certified interoperability between 802.11 wireless vendors.

Q2. 802.11b/g is the more popular wireless standard worldwide. One of your fellow network administrators on staff states that 11 separate RF channels are available for use across your corporate network. Is this true? Should you use all 11 channels? Justify your response.

Answer: The short answer to this question is that yes, 11 channels are available for use. However, it is not a good idea to use all 11 channels, because many of them overlap RF signals. In the U.S., you should use only channels 1, 6, and 11, because these channels have no overlap in RF signal.

Q3. List the three RF spectrums that are considered unlicensed bands. Which wireless standards are associated with each?

Answer: The three unlicensed RF bands are as follows: 900MHz: No mainstream wireless network technologies use this spectrum. 2.4GHz: 802.11b and 802.11g use this spectrum. 5GHz: 802.11a uses this spectrum.

Q4. Higher and lower frequencies on the RF spectrum provide different benefits. What are the benefits of higher frequencies (such as 2.4GHz and 5GHz) over lower frequencies?

Answer: Higher frequencies provide more bandwidth than the lower frequencies, but they also have a more limited range.

Q5. List at least three business benefits of using wireless networking.

Answer: There are many reasons why a business may be interested in wireless networking. Here are four: Elimination of stationary equipment Minimized office space due to roaming users Access to new cost-savings applications Cable installation and management cost

Q6. What Cisco-founded organization ensures compatibility between all 802.11 wireless vendor equipment?
A. 802.11
D. Wi-Fi Alliance

Answer: D. The Wi-Fi Alliance was founded by Cisco to ensure vendor interoperability on the 802.11 wireless standard. A vendor can obtain Wi-Fi certification, which assures customers that the equipment will interoperate with any other Wi-Fi certified device. Answer A is incorrect because 802.11 represents the wireless standard. Answer B is incorrect because the IEEE only manages and approves the wireless standards. Answer C is incorrect because the ITU-R is focused on regulating the 802.11 RF bands.

Q7. Which of the following wireless standards use the 2.4GHz RF band? (Choose two)
A. 802.11a
B. 802.11b
C. 802.11g
D. 802.11i

Answer: B, C. 802.11b and 802.11g share the 2.4GHz band. This allows the newer 802.11g standard to be backward-compatible with 802.11b. 802.11a uses the 5GHz band, and 802.11i is a security standard that does not use a specific band.

Q8. 802.11 wireless standards use which of the following transmission methods?
A. CSMA/CD, half duplex
B. CSMA/CD, full duplex
C. CSMA/CA, half duplex
D. CSMA/CA, full duplex

Answer: C. 802.11 uses CSMA/CA (collision avoidance) with half-duplex transmission. Because of this, the maximum rate of transmission is rarely attained when communicating on an 802.11 wireless network.

Q9. How many wireless channels are available in the U.S.A. for the 2.4GHz band without overlapping frequencies?
A. 1
B. 3
C. 11
D. 23

Answer: B. In the U.S., only three nonoverlapping channels are available for the 2.4GHz band. Europe has four nonoverlapping channels, because access to other unlicensed RF bands is available. The moral of the story? If you’re having trouble finding a free wireless channel in your area, move to0 Europe.

Q10. When wireless technology uses a higher frequency, what factors must you consider? (Choose two)
A. The higher frequency will allow for higher throughput
B. The higher frequency will restrict throughput
C. The higher frequency has more range
D. The higher frequency has limited range

Answer: A, D. The benefit of using a higher frequency is the ability to obtain more bandwidth (throughput). The drawback is the limited range of the higher frequencies.

Q11. You are the network administrator for Widgets, Inc., a worldwide distributing organization. You are planning on setting up a new wireless network for the organization. Which of the following are considerations for the new wireless network?
A. The geographic location of the office
B. The radio frequencies currently in use at the office locations
C. The radio channels currently in use at the office locations
D. The wireless cell configuration on the access point

Answer: A, B, C. When deploying a new wireless network, you must take into account the geographic region, because government regulations dictate what unlicensed RF bands and channels are available for public use. Likewise, you must also see what wireless RF bands and channels are free (not in use) in your location to get a clean signal. Answer D is incorrect because wireless cells are not configured on access points; rather, they are a design concept.

Q12. To provide for successful client roaming, how should wireless cells be configured?
A. Wireless cells should use the same RF band and channel
B. Wireless cells should use the same RF band but different channels
C. Wireless cells should use different RF bands but the same channel
D. Wireless cells should use different RF bands and channels

Answer: B. To provide for client roaming, wireless cells should use the same RF band but different channels. This allows a client to move between wireless access points without interference caused by overlapping signals.

Q13. Which of the following are advantages of 802.11a over 802.11b? (Choose two)
A. Increased throughput
B. Increased range
C. More channel diversity
D. Support for more clients

Answer: A, C. 802.11a has more bandwidth (54Mbps) compared to 802.11b (11Mbps) and more wireless channels available (up to 23). 802.11b does have more range than 802.11a because it uses the lower-frequency 2.4GHz band. Neither standard has any advantage as far as client support.

Q14. You are deploying a wireless network at a new office location. The office happens to be located next to an apartment complex with many existing wireless access points using all available channels in the RF band. Which agency would handle this situation?
C. Wi-Fi Alliance
D. None of the above

Answer: D. Although the ITU-R does manage the RF bands, it would not handle this specific situation. Boththe 2.4GHz and 5GHz bands are considered unlicensed for a reason: no entity will manage them. The solution to the apartment situation would be to find out if the apartment wireless devices are
transmitting at a higher-than-legal power or to change your company to the less-congested 5GHz band.

Q15. What is the largest cost savings that organizations typically find with wireless technology?
A. Elimination of stationary equipment
B. Minimized office space due to roaming users
C. Access to new cost-savings applications
D. Cable installation and management cost

Answer: D. Although wireless provides many conveniences for businesses, the primary cost savings can be found in the elimination of cable installation and management.

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