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


WHY WE NEED WIRELESS NETWORK ?

• 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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ADVANTAGES OF WIRELESS

• Cost reduction (no cabling

requirement)

• Flexibility (location independent)

• Productivity


WIRELESS TECHNOLOGIES

• 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


IEEE 802.11 WI-FI STANDARDS

• Set of media access control (MAC) and physical layer (PHY)

specifications for implementing wireless local area network

(WLAN) communication.


WIRELESS LAN vs WIRED LAN

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


WIRELESS NETWORK INTERFACE CARDS

• Provides wireless connection to

Access to wireless networks


WIRELESS MODEM

• Provides wireless broadband

connection for home users over

WI-FI


BUSINESS WIRELESS SOLUTIONS

• 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


WIRELESS ANTENNAS

• 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)


802.11 TOPOLOGY MODES

• Ad Hoc Mode : Direct wireless

connection without an AP

• Infrastructure Mode : Wireless

connection with an AP

Basic Service Area

Extended Service Area


AD HOC MODE

Laptop - 1 Laptop - 2


INFRASTRUCTURE MODE (BSA)

Laptop - 1

Laptop - 2

• Basic Service Area

• Number of APs : 1


INFRASTRUCTURE MODE (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








802.11 FRAME


CSMA / CA


CLIENT – ACCESS POINT CONNECTION

DISCOVER AP ( Active – Client must know SSID or Passive – AP advertises SSID

AUTHENTICATE (Open authentication (no pw.) or Shared Keys

ASSOCIATE


CONNECTION PARAMETERS

• 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


FREQUENCY CHANNEL SATURATION

• Frequency channels are used for

communication between sender

and wireless receiver devices

• If channel is used so much by

clients, it can saturate


FREQUENCY CHANNEL SATURATION (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


WIRELESS DOS ATTACKS

• 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


ROUGE ACCESS POINT

• Access point that has been installed on a

secure network without explicit

authorization to capture client data or

information such as MAC address


MAN IN THE MIDDLE ATTACK

• 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


HOW TO SECURE YOUR WIRELESS NETWORK ?

• Use shared key authentication (WEP / WPA / WPA2) and

encryption to secure your wireless network


4.4 Wireless LAN Configuration


WIRELESS ROUTER CONFIGURATION


WIRELESS ROUTER CONFIGURATION (cont.)











Technology

CCNA Wireless Lan (WLAN)