Friday

WLAN Devices

Most companies, when deploying wireless, use enterprise mode with ESA, where multiple APs provide coverage for the WLAN clients. The following sections discuss the basic configuration tasks for the APs and the clients, as well as common troubleshooting tips when clients have problems connecting to or communicating with APs.
Access Points
In computer networking, a wireless access point (WAP or AP) is a device that allows wireless communication devices to connect to a wireless network using Wi-Fi, Bluetooth or related standards. The WAP usually connects to a wired network, and can relay data between the wireless devices (such as computers or printers) and wired devices on the network. Cisco’s APs can be configured using a command-line interface (CLI), but it is actually much easier to use a graphical user interface (GUI). Cisco routers that support wireless include a component of Security Device Manager (SDM) that provides a GUI component for the wireless configuration component of the router. Wireless access has special security considerations. Many wired networks base the security on physical access control, trusting all the users on the local network, but if wireless access points are connected to the network, anyone on the street or in the neighboring office could connect. APs are layer 3 devices, and as such, they need a layer 3 address. Since TCP/IP is the de facto standard layer 3 protocol in the world today, your APs will need IP addressing information. This includes an IP address, a subnet mask, and a default gateway address. An access point can be either a main, relay or remote base station. A main base station is typically connected to the wired Ethernet. A relay base station relays data between remote base stations, wireless clients or other relay stations to either a main or another relay base station. A remote base station accepts connections from wireless clients and passes them to relay or main stations. Connections between "clients" are made using MAC addresses rather than by specifying IP assignments.
All base stations in a Wireless Distribution System must be configured to use the same radio channel, and share WEP keys or WPA keys if they are used. They can be configured to different service set identifiers. WDS also requires that every base station be configured to forward to others in the system.. This information can be assigned statically or dynamically using Dynamic Host Control Protocol (DHCP).
For the wireless communications, you’ll need to determine the protocol you’ll use for the APs: 802.11b, 802.11a, 802.11b/g, 802.11a/b/g, or possibly 802.11n. Finding APs that do 802.11a as well as other protocols requires that you have two radios in the AP. Cisco’s Aironet products support this feature as an option. You also might have to adjust the radio channels on the APs, the power adjustment, and the type of antennae if you are having signal problems
To secure your WLAN implementation, you’ll need to determine the following:
■ The SSID that will represent your WLAN
■ The security implementation:
■ WPA in either enterprise (preferably) or personal mode
■ WPA2 in either enterprise (preferably) or personal mode
Clients
A client is an application or system that accesses a remote service on another computer system, known as a server, by way of a network.[1] The term was first applied to devices that were not capable of running their own stand-alone programs, but could interact with remote computers via a network. These dumb terminals were clients of the time-sharing mainframe computer. In a Wireless LAN clients will need a wireless card, a driver for the card, and software to configure the card. Some operating systems include a utility for the software configuration, such as Microsoft Windows XP: Wireless Zero Configuration (WZC). WZC allows clients to discover the SSIDs within range automatically and to connect automatically to the AP that has the strongest signal. Clients, like APs, also need IP addressing information. For a SOHO network, it is common to set up the single AP as a DHCP server and have the AP assign addressing information to the clients; however, this does not scale well, nor work well, when using ESA with multiple APs. In this scenario, it is more common to have the AP forward DHCP requests from the clients to a real DHCP somewhere on the LAN network

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