Sybex CCNA 640-802 Chapter 12: Wireless Networks

Instructor & Todd Lammle

Chapter 12 Objectives

The CCNA Topics Covered in this chapter include:

• What is a WLAN?• IEEE Standards• CSMA/CD• ISM 2.4Ghz channels• UNII Band• BSS/ESS• Wireless Security

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Wireless LAN’s

• Transmitting a signal using the typical 802.11 specifications works a lot like it does with a basic Ethernet hub: They’re both two-way forms of communication, and they both use the same frequency to both transmit and receive, often referred to as half-duplex.

• Wireless LANs (WLANs) use radio frequencies (RFs) that are radiated into the air from an antenna that creates radio waves.

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Unlicensed Frequencies

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• 900MHz, 2.4GHz: Industrial, Scientific, and Medical (ISM) bands

• 5GHz: Unlicensed National Information Infrastructure (UNII) band.

802.11 Standards

Here are the most popular standards in use today:

• 802.11b: 2.4Ghz, maximum bandwidth of 11Mbps

• 802.11g: 2.4Ghz, up to 54Mbps• 802.11a: 5Ghz, up to 54Mbps

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802.11b CSMA/CA

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RTS: Request to SendCTS: Clear to Send

ISM 2.4 Ghz Channels

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• 14 different channels (each 22MHz) released by the FCC in the 2.4GHz range

• 3 non-overlapping channels

UNII 5Ghz Band

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• 12 non-overlapping channels (each 20MHz) released by the FCC in the 5GHz range

Range Comparisons

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BSS/ESS

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Wireless Security

All Wi-Fi Certified wireless LAN products are shipped in "open-access" mode, with their security features turned off.

• SSID (Service Set Identifiers), WEP (Wired Equivalency Protocol) and MAC authentication

• 802.11i• WPA (Wi-Fi Protected Access) and WPA 2

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Summary

– Summary– Open your books and go through all the

written labs and the review questions.– Review the answers in class.

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