Passive scanning (Beacons)
. . . .
Passive scanning (Beacons)
- In order for a station to be able to connect to an AP, it must first
discover an AP. - A station discovers an AP by either listening for an AP
(passive scanning) or searching for an AP (active scanning). - In passive scanning, the client station listens for the beacon frames that are continuously being sent by the APs, as seen in Figure 9.4.
- The client station will listen for the beacons that contain the same SSID that has been preconfigured in the client station’s software utility.
- When the station hears one, it can then connect to that WLAN.
- If the client station hears beacons from multiple APs with the same SSID, it will determine which AP has the best signal, and it will attempt to connect to that AP.
- It is important to understand that active and passive scanning can coexist on a network.
- A station can use either or both methods of scanning to discover the network.
- In an independent basic service set is deployed, all of the stations in Ad Hoc mode take turns transmitting the beacons since there is no AP.
Passive scanning occurs in an ad hoc environment, just as it does in a basic service set.
Figure 9.4 Passive scanning
Reference:
Coleman, David D.,Westcott, David A. CWNA: Certified Wireless Network Administrator Official Study Guide: Exam CWNA-106 Wiley.
Coleman, David D.,Westcott, David A. CWNA: Certified Wireless Network Administrator Official Study Guide: Exam CWNA-106 Wiley.
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