Sybex CCNA 640-802
Chapter 12: Wireless Networks
Chapter 12 Objectives
The CCNA Topics Covered in this chapter include:
•What is a WLAN?
•IEEE Standards
•CSMA/CD (CA? – collision avoidance, not detection)
•ISM (medical) 2.4Ghz channels
•UNII (Unlicensed National Information Infrastructure) band
•BSS/ESS
•Wireless Security
•WEP, WPA
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Wireless LAN’s
•Transmitting a signal using the typical 802.11 specificationsworks a lot like it does with a basic Ethernet hub: They’re bothtwo-way forms of communication, and they both use the samefrequency to both transmit and receive, often referred to ashalf-duplex.
•Wireless LANs (WLANs) use radio frequencies (RFs) that areradiated 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 Send
CTS: Clear to Send
You can’t observe a “collision” in theair or in the vacuum of space, so theonly way to deal with collisions is to“avoid” them. Ask for clearancebefore you send anything.
ISM 2.4 Ghz Channels
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•14 different channels (each 22MHz) released by the FCC in the2.4GHz range
•3 non-overlapping channels
UNII 5Ghz Band
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•12 non-overlapping channels (each 20MHz) released by theFCC in the 5GHz range
Range Comparisons
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BSS/ESS
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Cisco Unified Wireless
•The Cisco Unified Wireless Network is an integrated end-to-end solution that addresses all layers of the WLAN,from client devices and access points, to the networkinfrastructure, to network management, to the delivery ofadvanced wireless services integration and award-winning, worldwide, 24-hour product support. It deliversthe industry’s best wireless LAN security, innovation, andinvestment protection. It integrates innovative accesspoint technology with an award-winning centralizedmanagement system, intelligent control, real-timelocation services and a wide array of interoperable CiscoCompatible client devices. It is the only solution thatsupports next-gen wireless solutions like 802.11n andenterprise wireless mesh that offer greater performanceand extended reach for pervasive wireless connectivity.
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 EquivalencyProtocol) and MAC authentication
•802.11i
•WPA (Wi-Fi Protected Access) and WPA 2
• The End
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