Which three statements are true about implementing wireless LANs in the Company network
using Cisco devices? (Select three)
A.
Antenna power is a relative value reference to dBi.
B.
LWAPP allows encrypted communications between lightweight access points and
WLAN controllers.
C.
Characteristics of antennas are directionality, gain, and polarization.
D.
Power over Ethernet (PoE) is only available when a WLAN controller is integrated
into the network.
E.
The WLAN solution Engine (WLSE) is used to control lightweight access points.
One of the advantages of the lightweight WLAN solution is that the devices act indepently
Explanation:
DBi is a unit measuring the gain of an antenn
a. The reference level or dBi is the strength of the signal that would be transmitted by a nondirectional isotropic antenna i.e.radiates equally in all directions. This antenna exists as a
mathematical concept used only as a known reference to measure antenna gain per dBi. In
electronics, the term “gain” is often repeated but misunderstood. Gain implies increase e.g
20 dBi but without respect to where the increase originated.
LWAPP is a draft Internet Engineering Task Force (IETF) standard, authored by Cisco
Systems, that standardizes the communications protocol between lightweight access points
and WLAN systems such as controllers, switches, and routers. Its goals are to:
• Reduce the amount of processing within access points, freeing up their computing
resources to focus exclusively on wireless access instead of filtering and policy enforcement
• Enable centralized traffic handling, authentication, encryption, and policy enforcement for
an entire WLAN system
• Provide a generic encapsulation and transport mechanism for multivendor access point
interoperability, using either a Layer 2 infrastructure or an IP-routed network
When a Cisco LWAPP-enabled access point boots up, it immediately looks for a wireless
LAN controller within the network. After it finds a wireless LAN controller, the LWAPPenabled access point sends out encrypted “neighbor” messages.
An antenna gives the wireless system three fundamental properties: gain, direction and
polarization. Gain is a measure of increase in power. Gain is the amount of increase in
energy that an antenna adds to a radio frequency (RF) signal. Direction is the shape of the
transmission pattern. Polarization is the physical orientation of the element on the antenna
that actually emits the RF energy. An omnidirectional antenna, for example, is usually a
vertical polarized antenna.
References:
http://wireless-network.wireless-computer-networking.com/dBi.htm
http://www.cisco.com/en/US/tech/tk722/tk809/technologies_tech_note09186a00807f34d3.sh
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