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71.
An AP has been configured to use channel 1 with a transmit power of 20 dBm. With
the AP located in the center of the lobby, you have determined that its signal will
reach all locations in the lobby area. However, some users with small battery-operated
devices report connectivity problems when they move toward the outer walls of the
lobby. Which of the following approaches will probably fix the problem? (Choose
two.)
- A.Increase the AP's transmit power to increase its range
- B.Increase the client device's transmit power
- C.Adjust the client device's roaming algorithm
- D.Enable some lower data rates on the AP
- Answer & Explanation
- Report
Answer : [B and D]
Explanation :
Explanation :
| If you have already tested the AP's signal and determined that it reaches every location in the lobby area, the problem is not that the AP's transmit power is insufficient. Instead, the problem is occurring because the small client devices must be using a transmit power that is lower than that of the AP. In other words, the client's signals are not strong enough to reach the AP, so the two have asymmetric power levels. One solution is to increase the client's transmit power level (if possible) to be identical to the AP's. Another solution is to lower the data rate on the AP so that its signal will be usable at the client's location. A lower data rate uses less complex modulation and coding schemes, which stay intelligible at farther distances. |
72.
Suppose that an AP is configured to offer the following data rates to its clients: 2, 5.5,
6, 9, 11, 12, 18, 24, 36, and 48 Mbps. Which one of the following strategies should
be used to reduce the AP's cell size?
- A.Enable the 1-Mbps data rate
- B.Enable the 54-Mbps data rate
- C.Disable the 36- and 48-Mbps data rates
- D.Disable the 2-Mbps data rate
- Answer & Explanation
- Report
Answer : [D]
Explanation :
Explanation :
| The 1-Mbps data rate is already disabled, which limits the cell size to some extent. You can reduce it further by disabling the 2-Mbps data rate. |
73.
All the APs on the second floor of a building are part of a single ESS. Each AP has
been configured with a transmit power level of 14 dBm. In addition, each AP has been
configured to use a non-overlapping channel that is different from its adjacent neighbors. All APs have been configured to offer only the 24-, 36-, 48-, and 54-Mbps data
rates; all other rates are disabled. One day, one of the APs fails and someone replaces
it. Afterward, users begin to call and complain about poor performance and roaming.
You discover that the problems are not occurring in the area covered by the replacement AP; instead, they are occurring about two APs away from it. Which one of the
following could be causing the problem?
- A.The replacement AP has its radios disabled.
- B.The replacement AP is using a transmit level of 1 dBm.
- C.The replacement AP is using the 1- and 2-Mbps data rates.
- D.The replacement AP is new and cannot be causing the problem.
- Answer & Explanation
- Report
Answer : [C]
Explanation :
Explanation :
| If the problem is occurring some distance away from the replacement AP, the replacement AP must be working correctly within its immediate area. If the replacement had a 1-dBm transmit power, it could not be causing any interference at a great distance away. The problem is likely occurring because the lowest data rates have been enabled on the AP. The lower rates effectively extend the replacement AP's cell size into the cells of other APs farther away. If the channels are identical, the replacement could be causing co-channel interference in other cells, degrading client performance and roaming. |
74.
Which one of the following determines when a wireless client will roam from one AP
to another?
- A.The current AP detects a weak signal coming from the client and forces the client to roam.
- B.The next AP overhears the client's signal and asks it to roam.
- C.The client's roaming algorithm reaches a threshold in signal quality.
- D.The client loses its IP address.
- Answer & Explanation
- Report
Answer : [C]
Explanation :
Explanation :
| Roaming is entirely up to the client. The client runs a roaming algorithm that compares current conditions to a threshold. When the signal quality or other factors drop below the threshold, the client tries to roam. |
75.
Which one of the following 802.11 frames is used to trigger a roam from one AP to
another within an ESS?
- A.Association request
- B.Disassociation request
- C.Probe
- D.Reassociation request
- Answer & Explanation
- Report
Answer : [D]
Explanation :
Explanation :
| Whereas an association request is used to join a BSS, a reassociation request is used to move from one BSS to another within the same ESS. |
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