CCNA Wireless Lan (WLAN)

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4- Wireless LAN
4.1 Wireless LAN Overview
4.2 Wireless LAN Operations
4.3 Wireless LAN Security
4.4 Wireless LAN Configuration

4.1 Wireless LAN Overview

WHYWENEEDWIRELESSNETWORK?
• Today, mobility is very important
• People want to connect to a LAN or
internet from almost everywhere
( Home, cafe, stadium etc. )
• Solution : Wireless Network

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ADVANTAGESOFWIRELESS
• Cost reduction (no cabling
requirement)
• Flexibility (location independent)
• Productivity

WIRELESSTECHNOLOGIES
• WI-FI : Network connection up to
7 Gbps (IEEE 802.11 Standards)
• Blueetooth : Up to 14 Mbps
transmission (IEEE 802.15)
• Wi-MAX : Up to 50 km wireless
broadband connection (Up to
1gbps)
• Cellular Broadband : 3G, 4G
• Satellite Broadband : Broadband
from directional satellite dish

IEEE802.11WI-FISTANDARDS
• Set of media access control (MAC) and physical layer (PHY)
specifications for implementing wireless local area network
(WLAN) communication.

WIRELESSLANvs WIREDLAN
Characteristic 802.11 WLAN Ethernet LAN
Physical Layer Radio Frequency (Very Low) Cable
Media Access Collision Avoidance Collision Detection
Availability Everybody in the range of AP Cable connection required
Signal Interference Yes Inconsequential

WIRELESSNETWORKINTERFACECARDS
• Provides wireless connection to
Access to wireless networks

WIRELESSMODEM
• Provides wireless broadband
connection for home users over
WI-FI

BUSINESSWIRELESSSOLUTIONS
• Provides wireless LAN connection
for corporate users
• Autonomous AP : Access points
are configured individually
• Controller-Based AP : Access
points are managed by a
controller. Controller can provide
a single configuration for multiple
APs
R1
SW1
PC2PC1
AUTONOMOUS OR
CONTROLLER-BASED AP
PC3
Laptop - 1
Laptop - 2
Laptop - 3

WIRELESSANTENNAS
• Omnidirectional : Radiation cone
is 360 degrees, working in all
directions
• Directional : Refers to signal
coverage in a specified direction
• Yagi : Used for moving Wi-Fi
signals to longer distances
(Directional)

802.11TOPOLOGYMODES
• Ad Hoc Mode : Direct wireless
connection without an AP
• Infrastructure Mode : Wireless
connection with an AP
 Basic Service Area
 Extended Service Area

ADHOCMODE
Laptop - 1 Laptop - 2

INFRASTRUCTUREMODE(BSA)
Laptop - 1
Laptop - 2
• Basic Service Area
• Number of APs : 1

INFRASTRUCTUREMODE(ESA)
• Extended Service Area
• Number of APs : 2 or more
R1
SW2
PC2 PC3Laptop - 1
Laptop - 2
Laptop - 3
SW1
PC1

4.2 Wireless LAN Operations

802.11FRAME

CSMA/ CA

CLIENT– ACCESSPOINTCONNECTION
DISCOVER AP ( Active – Client must know SSID or Passive – AP advertises SSID
AUTHENTICATE (Open authentication (no pw.) or Shared Keys
ASSOCIATE

CONNECTIONPARAMETERS
• SSID : Used as an identifier for a wireless
LAN, and is intended to be unique for a
particular area (Name of AP)
• Security Key : Used for client
authentication
• Security Mode : WEP / WPA / WPA2
• Network Mode : 802.11a/b/g/n/ac/ad
• Channel Settings : Frequency band

FREQUENCYCHANNELSATURATION
• Frequency channels are used for
communication between sender
and wireless receiver devices
• If channel is used so much by
clients, it can saturate

FREQUENCYCHANNELSATURATION(cont)
• To decrease the saturation ;
 Direct-sequence spread spectrum (DSSS) : Spread
radio energy over a channel (802.11b)
 Frequency-hopping spread spectrum (FHSS) : Use the
whole band in small intervals (802.11)
 Orthogonal Frequency-Division Multiplexing
(OFDM) : Multiple transmissions simultaneously over
a single channel (802.11a/g/n/ac)

4.3 Wireless LAN Security

WIRELESSDOSATTACKS
• DOS attacks are easily executed in a
wireless network.
• Emitting a very strong RF interference on
the channel in which the wireless
network is operating on will increase the
noise on that channel and thus causing
interference to all wireless networks that
are operating at / near that channel

ROUGEACCESSPOINT
• Access point that has been installed on a
secure network without explicit
authorization to capture client data or
information such as MAC address

MANINTHEMIDDLEATTACK
• Attacker secretly relays and
possibly alters the communication
between two parties who believe
they are directly communicating
with each other.
• An attacker within reception
range of an unencrypted Wi-Fi
wireless access point can insert
himself as a man-in-the-middle

HOWTOSECUREYOURWIRELESSNETWORK?
• Use shared key authentication (WEP / WPA / WPA2) and
encryption to secure your wireless network

4.4 Wireless LAN Configuration

WIRELESSROUTERCONFIGURATION

WIRELESSROUTERCONFIGURATION(cont.)

CCNA Wireless Lan (WLAN)

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