CCNA Complete Guide 2nd Edition.pdf - Cisco Learning Home

- Upgrading from 802.11b to 802.11g requires purchasing of new wireless hardware instead of
software upgrade, as 802.11g radios use different chipsets in order to deliver higher data rates.
- 802.11b uses the Direct Sequence Spread Spectrum (DSSS) modulation technique for data
transmission which is not as robust as the Orthogonal Frequency Division Multiplexing
(OFDM) modulation technique used in both 802.11g and 802.11a.
Note: When 802.11g devices are operating at the 802.11b transfer rates, they are actually using
the same modulation technique as 802.11b uses – DSSS. A WLAN with 4 802.11g clients and 1
802.11b client that connected to the same access point are forced to run the 802.11b CSMA/CA
mechanism which really makes throughput suffer. It is recommended to enable the 802.11g-only
mode on an access point in order to optimize performance.
- 802.11n is a new WLAN standard that allows even higher speeds at greater distances. 802.11n is
built upon the 802.11 standards by adding Multiple-Input Multiple-Output (MIMO), which
employs multiple transmitter and receiver antennas to achieve higher data rates and throughput.
802.11n can have up to 8 [smart] antennas, but most of today’s 802.11n access points use 4 – 2
for transmitting simultaneously while another 2 for receiving simultaneously. 802.11n uses wider
channel bandwidth (40MHz) for operation compared to 22MHz as in legacy 802.11 operation.
- The 802.11n standard is not yet been ratified, which means that the “Pre-N” products on the shelf
today are proprietary.
- Bluetooth is another wireless standard for short-range radio connections between laptops,
mobiles phones, digital cameras, headsets, and other portable devices. It can be considered as a
standard for Personal Area Networks (PANs).
- Cisco offers a complete line of indoor and outdoor wireless LAN solutions, eg: access points,
WLAN controllers, WLAN client adapters, security and management servers, wireless
management devices, as well as wireless integrated switches and routers.
- An Infrastructure mode WLAN is either as a Basic Service Set (BSS) with an access point or as
an Extended Service Set (ESS) with multiple access points where multiple BSSs connected by a
common distribution system with all configured with the same SSID for roaming purposes.
Non-root devices (eg: bridges, repeater APs) can only connect to a root device as repeaters.
- Cisco Unified Wireless Network Solution (UWN) allows intelligent Cisco access points and
Cisco WLAN Controllers (WLCs) to be managed through the controller web interface, the
controller itself, or via the Cisco Wireless Control System (WCS). The Cisco WCS works in
conjunction with Cisco Aironet Series Lightweight Access Points, Cisco WLAN Controllers, and
Cisco Wireless Location Appliance to provide a centralized management platform for the
planning, designing, configuring, controlling, managing, and monitoring of enterprise WLANs.
- The Cisco WCS can manage the WLAN controllers and eventually the entire WLAN from a
single GUI interface. It can also provide a detailed insight into the network coverage, the
trending of network statistics, device locations, etc.
- An access point in this type of network requires zero configuration after initial installation,
which means that it can be connected in an indoor or outdoor environment and configured
automatically based on the information provided by WLAN controller. It will even check for
channel overlapping and interference and assign a non-overlapping channel. If it detects an
overlapping channel within its area, it will lower its transmitting level to limit interference – the
automated RF/radio management and automated channel planning features.
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