Hardware Issues


Hardware can play a major issue in poor WLAN performance. This can range from outdated system software on your APs to loose cabling on your antennas.

Firmware

Out-of-date firmware is an often overlooked problem with radio performance.

Sometimes the firmware on your AP becomes out-of-date as new features are added. You can update the firmware if you load the firmware image from the manufacturer.

You can try to reset the AP's configuration. Disconnect power for a few minutes, and then reconnect. Alternately (as in the case of the Cisco 1100 APs), press the MODE button for 30 seconds. This resets the firmware image to its default settings.

You can also update your AP's firmware if you download the newest version from the Cisco website. Follow these steps to install it onto your AP:

Step 1.

Navigate to the Software Upgrade screen (follow System Software > Software Upgrade).

Step 2.

Click the tab at the top of the screen to pick an upgrade method. Figure 14-1 shows the HTTP Upgrade tab selected, although you can also upgrade via TFTP.

Figure 14-1. Upgrading an AP's Firmware


Step 3.

Click the Browse button to select the updated firmware file.

Step 4.

Click Upgrade to install the system software.

Don't overlook the firmware on your client devices, too. You should make sure to upgrade AP firmware and adapter firmware. Also check release notes on firmware. This can tell you what the firmware updates, including any bug fixes.

Configuration

Many performance and connectivity problems stem from configuration issues. If you have problems with WLAN performance and connectivity, check this place first.

You can spread out these settings through various screens in your AP's configuration screens or you can manage them via the command-line interface. Table 14-3 lists and explains the usual sources of configuration problems.

Table 14-3. Common Configuration Problems

Setting

Description

Service Set Identifier (SSID)

Unless the AP and client use the same SSID, they cannot communicate with one another.

Data Rate

If devices are configured to use different data rates, they cannot communicate. Check the setting on all devices to ensure that they use the same data rate.

Distance[*]

For bridges, the Distance setting is important to set because it lets the bridges know that there is a given amount of lag time between the bridge's transmission and the receiving bridge's reception.

Frequency and Channel

Cisco APs, by default, scan the radio spectrum to locate an ideal channel and radio frequency to use. However, if this setting is disabled, clients and APs might use different frequencies. For best results, check to ensure that the clients and APs are on the same channel. The best practice is to ensure that the APs and clients are configured to automatically use the same frequency.


[*] This setting is commonly made in kilometers, not miles.

Signal Problems

Radio signals are disrupted for several reasons. The most common include interference, which we discuss in preceding chapters. Interference comes from other RF sources (cordless telephones or neighboring WLANs, for instance) or from electromagnetic interference (from non-communications equipment, such as microwave ovens).

Other factors, however, can have an impact on your WLAN's performance. Although you might blame typical problems on radio interference, you might check the cabling, instead.

Cable Type

When you connect bridges or APs that are situated far from their antennas, it's best to keep the antenna cabling as short as possible, because signal strength degrades on long runs of cabling. Cisco provides a tool to help determine the maximum distance over which two bridges can communicate. The link to the Antennae Calculation Spreadsheet is contained in the "Other Resources" section in this chapter.

Installation Issues

When cables connect your antennas to your wireless devices, problems can occur. Check your cabling, with a special eye for the following:

  • Loose connectionsPoorly seated connector cables can cause poor signal quality.

  • Exposed connectorsSeal connectors that are exposed to the elements.

  • Damaged cables Bent, crimped, or otherwise mutilated cabling can cause signal degradation.

  • Power cablesElectromagnetic interference that comes from nearby power cables can cause signal degradation.




Cisco 802.11 Wireless Networking Quick Reference
Cisco 802.11 Wireless Networking Quick Reference
ISBN: 158705227X
EAN: 2147483647
Year: 2005
Pages: 126

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