User's Guide

• A common perception is that wireless devices must be detected and monitored throughout a given
property. This becomes impractical in many cases. A more practical approach is one that protects
the wired network while using more sane decisions for monitoring.
Sensor Quantity and Placement
Application choice will significantly impact the sensor density and sensor placement. For example,
rogue detection in a no wireless zone needs fewer sensors as even sporadic emanations from a wireless
device, at the lowest data rate and longest range, can reveal the presence of a rogue. As the
applications become more complex, they may require a representative sample of frames or meet
certain minimum signal level thresholds, increasing the sensor density requirement.
Using these factors in baseline decisions with regard to sensor placement, the following coverage area
guidelines may be applied to establish an eective deployment.
Application RSSI
Rogue Detection > -90dBm
Policy Enforcement > -80dBm
Mitigation (Termination) > -70dBm
Location Tracking Every device has to be seen by three or more sensors and/or
infrastructure APs on the same floor plan.
Sensors that may be exposed to harsh environments can be placed in accessory enclosures (NEMA-4)
that protect the sensor and provide code, regulatory compliance, or both.
Power and Data Cabling
Sensors are often placed in areas that take advantage of pre-existing power and data cabling. These
areas include wiring closets and other areas where IDFs may be located. Where these locations are
somewhat shielded from the wireless environment, the sensor may be extended to just outside of these
spaces using standard power cords and pre-terminated data cables, obviating the need for additional,
costly fixed runs. Choosing facilities that come as close to centrally locating the sensors in the intended
monitoring space should be done when practical. In instances where wiring closets, IDFs, or both are
not ideally located for sensor placement, sensors may take advantage of Power Over Ethernet, either
from a single power injector or a compliant switch. PoE injectors are available from Extreme Networksi.
If there are gaps in coverage, or if deployment cost is a factor (due to the required density of sensors or
the cost of wiring to place sensors in strategic locations), there are several relatively inexpensive
remedies. Where wiring for placement in an ideal location is impractical, employ additional sensors to
correct as necessary. FCC Rules regulate the use of antennas as aids to reception for the sensors, in
regard to the sensors 802.11 component. If antennas would greatly enhance the overall deployment,
contact Support for guidance on the best approach for antenna application, considering both
regulatory guidelines and the physical design of the sensors.
In either case, always use facility floor plans to indicate where sensors are placed and to indicate areas
where a coverage test was done.
Planning Your Sensor Placement
This section discusses the planning the placement of sensors.
Legacy Content
Planning Your Sensor Placement
Extreme AirDefense User Guide for version 10.5. 1381