Lab Manual for CWNA Guide to Wireless LANs, Second Edition
Lab Manual Solutions 5-1
Chapter 5 Solutions
Activity Questions, Lab 5-1
Lab 5.1 Note: The instructor access point kilo-lima should be connected to the same network as the
student access points, but far enough away from the classroom so that when the students walk
away from their access point they will lose connectivity before they can connect to kilo-lima. I
recommend connecting one of the student’s access points in the classroom and connecting kilo-lima
in another classroom to test this before class. Also, make sure the instructor access point is
connected in a locked classroom or office where it won’t be stolen. The students will need the MAC
address of kilo-lima before this lab.
10. Are both of your laptops connected to your access point using the Twowap profile? What is your
connected speed? What is your IP address?
Answer: Hopefully, yes; Varies; Varies
12. What is displayed in the pop-up window?
Answer: Indication that laptop is not connected
13. What is displayed in the pop-up window now? What is your IP address?
Answer: Now connected; Should be the same as recorded in #10
14. Were you successful?
Answer: Hopefully, yes
16. What is your signal strength? What is your connected speed?
Answer: Varies; varies
Review Questions, Lab 5-1
1.
How is signal strength related to mobility?
Answer: Signal strength decreases as the mobile device moves away from the access point.
2.
What is the benefit of configuring the MAC address of the access point in the client profile?
Answer: Guarantees you will associate with the correct access point if more than one access point is
using the same SSID
3.
If your IP address remained the same between access points, why do you think it did?
Answer: Because the access points communicate with each other on the network
4.
You walked away from one connection in the lab activity and associated with another. Why is this
not considered true roaming?
Answer: You lost your connection, and with true roaming you shouldn’t.
5.
When the signal gets weak, the client device starts scanning. Why does this happen?
Answer: It is looking for an access point to associate with.
Activity Questions, Lab 5-2
Lab 5.2 Note: The instructor access point kilo-lima should be connected to the same network as the
student access points, and allow the students to walk away from their access point and then
connect to kilo-lima without losing connectivity. I recommend connecting one of the student’s
access points in the classroom and connecting kilo-lima in another classroom or office to test this
before class.
Also, make sure the instructor access point is connected in a locked classroom or office where it
won’t be stolen. The students will need the IP address of the instructor laptop (kilo or lima) that is
acting as the FTP server. I use 3CServer because it is free and easy to configure, but any FTP
software should work. Make sure the instructor laptop with the FTP software is connected
wirelessly to kilo-lima. I have them sitting side by side for this lab. The FTP software should be
Lab Manual for CWNA Guide to Wireless LANs, Second Edition
Lab Manual Solutions 5-2
running and there should be a very large file named tournament.ssf (about 77 MB) on the desktop
of the FTP server. Any very large file will do. Just make sure you name it tournament.ssf to match
the lab instructions. The server software should be configured to point to the desktop as the
location for uploads and downloads. Anonymous access should be allowed and overwrite files
should be allowed. Try this lab before class to make sure your location provides for roaming and
that the FTP software is working.
1.
What is your IP address?
Answer: Varies
3.
With which access point are you associated? What is your IP address? What is your connected
speed? What is one factor in making the decision to jump to another access point?
Answer: Kilo-lima; Same as recorded in #1; Should be excellent; SNR
7.
What is the reported throughput in kilobytes per second?
Answer: Varies
8.
What is the reported throughput in megabits per second?
Answer: Varies
9.
Calculate the percentage of the rated bandwidth you experienced during the download by dividing
the reported throughput recorded in Step 8 by the rated bandwidth of your connection.
Answer: Varies
Review Questions, Lab 5-2
1.
What is the difference between layer 2 roaming and layer 3 roaming?
Answer: Layer 2 roaming involves access points on the same subnet and layer 3 roaming means the
access points are on different subnets.
2.
How much cell overlap is required for layer 2 roaming to work?
Answer: 20%
3.
Why should we expect a lower throughput rate when roaming?
Answer: Because when you associate with a different access point, the coordination between the
access points increases overhead
4.
The decision to roam from one access point to another largely depends on the signal-to-noise ratio.
True or False?
Answer: True
5.
How does the client know where to roam?
Answer: Scanning
Activity Questions, Lab 5-3
4.
What is the default power save mode for your adapter?
Answer: CAM
6.
What differences do you see between the CAM laptop and the FastPSP laptop? Do you notice any
difference in LED activity on the adapters?
Answer: More activity with CAM; More light activity with CAM
8.
Once again, compare the activity onscreen and the LED activity on the adapters. Can you tell that
Max PSP mode conserves the most power?
Answer: Even less activity when using MaxPSM; Yes
10. Can you adjust the power save mode on this adapter when you are in ad hoc mode?
Answer: No
Lab Manual for CWNA Guide to Wireless LANs, Second Edition
Lab Manual Solutions 5-3
Review Questions, Lab 5-3
1.
What three power options are available with the Cisco Aironet a/b/g wireless adapter?
Answer: CAM, Fast PSP mode, and MaxPSM
2.
Which mode offers the best throughput and why?
Answer: CAM, because the adapter is always awake
3.
Which mode prolongs the laptop battery the most and why?
Answer: MaxPSM, because the adapter sleeps the most
4.
How would you decide which mode to use for your wireless client?
Answer: Depends how often your mobile device is without AC power
5.
Which mode do you think would be best for a wireless desktop computer? Why?
Answer: CAM, because you don’t have to worry about running on the battery; you always have AC
power
Activity Questions, Lab 5-4
9.
What is the name of the SSID you configured? What type of authentication is configured for this
SSID?
Answer: Varies; Open
19. Why did you lose connectivity?
Answer: Client profile is for shared authentication and the access point is using open authentication.
20. Double-click the Infrastructure Mode profile to activate it. Did you reconnect?
Answer: Hopefully, yes
Review Questions, Lab 5-4
1.
What are the two authentication methods required by the 802.11 standard?
Answer: Open and shared key
2.
Which of these two authentication methods is considered more secure, and why?
Answer: Open, because shared key shares the key in both encrypted and unencrypted form, giving
the attacker enough information to break the key
3.
What are the two WEP key strengths currently supported by 802.11?
Answer: 40-bit (64) and 128-bit (104)
4.
Why did you lose connectivity in the lab activity when you configured your access point for shared
key authentication?
Answer: Because the client device was still configured for open authentication
5.
List the WEP key strengths with their corresponding required number of hexadecimal digits.
Answer: 40-bit requires a 10 hex digit key and 128-bit requires a 26 hex digit key
Activity Questions, Lab 5-5
Lab 5.5 Note: AiroPeek uses a special driver that can interfere with other special sniffing drivers.
Once you run AiroPeek on a laptop, you will need to reboot the laptop in order for it to connect to
the wireless network correctly. At the end of the lab manual or class, AiroPeek and the special
drivers are removed to prepare the equipment for the next class, but if you want to get rid of the
special driver, just go to the properties of the Cisco a/b/g card and click Rollback Driver.
31. What channel are you using?
Answer: Varies according to Table 4-5 in Lab 4.4
32. What is the default fragmentation threshold for your access point? In terms of frame sizes, what does
this fragmentation threshold correspond to?
Lab Manual for CWNA Guide to Wireless LANs, Second Edition
Lab Manual Solutions 5-4
Answer: 2346 bytes; Max wireless frame size for 802.11
42. How many packets were received in the 30-second capture? What was the average utilization in
Kbps? How many total errors were logged?
Answer: Varies; varies; varies
47. How many packets were received in the 30-second capture? What was the average utilization in
Kbps? How many total errors were logged?
Answer: Varies; varies; varies
49. How many packets were received in the 30-second capture? What was the average utilization in
Kbps? How many total errors were logged?
Answer: Varies; varies; varies
51. According to the packet size tables, what happened to the percentage of packets sized 256 to 511
bytes as the fragmentation threshold was reduced? Does this make sense? Why or why not?
Answer: Increased; yes; forcing smaller packets because the fragmentation threshold is being reduced
52. According to Table 5-4, what was the effect of reducing the fragmentation threshold on the number
of packets received? What was the effect of reducing the fragmentation threshold on errors? Do your
results support or refute the hypothesis that smaller fragments will reduce collisions and errors up to
a point, but at some point will create enough overhead that performance will be degraded? Which
fragmentation setting would you recommend on your system if audio streaming is frequently used?
Answer: Increase; decreases errors; hopefully support; varies
Review Questions, Lab 5-5
1.
What is the maximum size of an 802.11 wireless frame?
Answer: 2346 bytes
2.
Why does CSMA/CA have more overhead than CSMA/CD?
Answer: Every frame has overhead and every frame must be ACK’d.
3.
What is the relationship between wireless frame size and probability of collisions?
Answer: The larger the frame, the higher the probability of collisions
4.
What is the advantage of using relatively smaller wireless frames?
Answer: Less collisions
5.
What is the advantage of using relatively larger wireless frames?
Answer: Less overhead