Cisco Aironet Linux Client FAQ

Introduction

This document provides questions and answers about Aironet Linux clients.

Refer to Cisco Technical Tips Conventions for more information on document conventions.

Q. Where can I find the latest utilities, drivers, and firmware for my Linux client?

A. Cisco Aironet equipment operates best when all the components are loaded with the most current version of software. Software updates are available at the Cisco Downloads - Wireless Software Page.

Q. How do I update the software for my Linux client?

A. There are three pieces to the client software:

1. Radio firmware on the card—The radio firmware resides on the client device, and in the case of the PC Card, is actually removed from the PC when the card is removed.

2. Client driver for the operating system —The client driver is the software that manages interactions between Linux (or other operating system) and the hardware.

3. Aironet Client Utility—The Aironet Client Utility is a utility to manage the card and the radio.

These three pieces of software have different functions, but work together in order to provide wireless connectivity to your client. They should always be updated to the most recent versions available. The client driver and the ACU are bundled together on the Linux utilities page. The firmware is a separate download from the hardware pages for the radio. Refer to the Release Notes for Cisco Aironet Wireless LAN Adapters and locate the Installation Instructions section in the Contents for information on how to update these items.

Refer to Install Linux Drivers and Utilities for the Cisco Aironet 340/350 Series Client Adapters for more information.

Q. What distributions and kernels does the Linux client run on?

A. The Linux driver runs on most distributions, and kernels 2.2.x and 2.4.x are supported. While there is a precompiled driver for RedHat 7.1 that runs kernel 2.4.2-2, the source is included so that you can compile binaries under any of the supported kernels. You should use PCMCIA-CS version 3.1.22 or later for 340 series clients, and 3.1.26 or later for 350 series clients.

Q. When I try to launch the Aironet Client Utility (ACU) from a terminal window, I get the No Radio Found error message. What is the problem?

A. If the driver for the card is not installed properly or not loaded, the ACU cannot find the card, and displays this error. Re-run the installation script with sh ./cwinstall from the directory where you unzipped the AIROLINUXvxxxxx.tar.gz file.

Q. When I try to compile the driver from the PCMCIA-CS directory, I get memcpy errors. Where do I look to find the problem?

A. This can come from a number of sources, but most commonly, it is a problem with either of these sources:

• The PCMCIA-CS source

• Your kernel source

Make sure that the PCMCIA-CS source is at least 3.1.22 (3.1.26 or later is preferred). Also, verify that the running kernel and your kernel source tree are the same.

Q. I use a PCI card, and the readme.txt file says I should configure linuxconf in order to load the module airo.o for the PCI card, but if I do it, it gives me an error that the module cannot be found. What is the problem?

A. While the name of the module is actually airo.o, linuxconf looks for just airo and looks for a file that ends with .o in the modules directory. Make sure that the airo.o file resides in your modules directory. If it does not, go to your PCMCIA-CS directory and re-run the make config, make all and make install procedures as directed in the ./cwinstall script.

Q. How do I make a Client Card work with a non-Cisco access point?

A. The access point, not the client, controls interoperability. Make sure that the access point does not use any proprietary extensions or requires firmware specific to the manufacturer products. Also make sure that the access point is 802.11b compliant.

Q. The access point has an entry in the association table for my PCMCIA card, but I cannot get a dynamic IP address. What is the problem?

A. The most common cause of this behavior is the inability of the PC to communicate with the card through the PCMCIA socket. Check the driver for your PC Card Socket. If it is a CardBus driver, it is most likely 32-bit only. The Cisco Aironet card requires 16-bit access, and if the modules for the socket are compiled for 32-bit mode only, you must recompile them into 16-bit capable versions. Check lsmod in order to verify that the airo and pcmcia_core modules are loaded.

Q. When my PC card is passing traffic, the speakers in my laptop buzz. What is the problem?

A. This problem comes from inadequate shielding around the PCMCIA socket itself. The radio energy of the card passing traffic leaks over into the speakers, since it is not sufficiently contained in the card socket, and presents itself as a buzz in the speakers. Your card is passing traffic. It is not a problem with the card; it is the socket. Resolution needs to come from the manufacturer of the laptop who chose not to shield the socket.

Q. Where can I find help to install my Client Card?

A. Refer to Cisco Aironet Wireless LAN Adapters Installation and Configuration Guide for Linux.

Q. Can I remove the PCMCIA card radio module from an Aironet PCI client adapter and use it as a PCMCIA client adapter?

A. No. This is not supported in any version of the hardware. Because the radio card is set to a different I/O mode, the card is not recognized by the Operating System. There is no known way to bypass this.

Q. What are possible sources of interference for the Radio Frequency link of my Client Card?

A. Interference can come from a number of sources, which includes 2.4 GHz cordless phones, improperly shielded microwave ovens, and wireless equipment manufactured by other companies. Police radar, electrical motors and moving metal parts of machinery can cause interference, too. Refer to Troubleshooting Problems Affecting Radio Frequency Communication for more information.

Q. Can I run two computers together without an Access Point?

A. From the Aironet Client Utility (ACU) you can configure the clients to run in AD HOC mode. This is only a peer-to-peer connection. One PC becomes parent the other is the child.

Q. Do I need special hardware to support encryption?

A. The specific hardware model of the unit determines the level of encryption.

• 341 and 351 models only support 40-bit encryption

• 342 and 352 models support both 40 and 128 bit encryption

Q. Which devices can associate with a Client Card?

• Client to Access Point

• Client to Bridge (in Access Point mode)

• Client to Base Station

• Client to Client (in AdHoc mode)

Q. At what frequency does a Client Card communicate?

A. In the US, wireless LAN radios transmit and receive in one of 11 channels within the 2.4 GHz frequency. This is a public frequency, and is unlicensed by the FCC.

Q. How do I secure the data across the radio link of a Client Card?

A. Enable Wired Equivalency Protocol (WEP) in order to encrypt the payload of packets sent across a radio link.

Q. How many clients can associate to an Access Point?

A. An Access Point has the physical capacity to handle 2,048 MAC addresses. But, given that the access point is a shared medium, and acts as a wireless hub, the performance of each user is degraded as the number of users increases on an individual access point.

Q. What is the typical range for a Client Card?

A. In an optimal installation, range can be up to 300 feet. The answer depends on many factors, such as:

• data rate (bandwidth) desired

• antenna type

• cable length

• device that receives the transmission

Q. How do I set the Client Card back to its factory default settings?

A. Launch the ACU and choose Commands, then Edit Properties. On each window, choose Defaults.

Q. Are the 340 and 350 series products interoperable?

A. Yes. The major difference between the two product lines is the power of the radio, with the 350 series that has the stronger radio at 100 milliwatts. Whereas 340 series products have 30 milliwatts radio. In a mixed installation, the shorter range of the 340 series prevails.

Q. Why does my Client Card not associate to the closest Access Point?

A. If there are multiple access points in your wireless topology, your client maintains an association with the access point it originally associated with until it loses keepalive beacons from that access point. It then seeks out another access point and attempts to associate to it, provided that the client has sufficient rights and authorization on the new access point.

Also, a wireless client associate to an AP not based on the distance between itself and the AP. But, instead there are several factors, which include the current load on the AP, the received signal strength from an AP and so forth, to decide the association.

Q. Does the Linux driver for the Cisco Aironet 350 Series Wireless Card support Wi-Fi Protected Access (WPA) encryption?

A. No, the Linux drivers for the Cisco Aironet 350 Series Wireless Card do not support WPA.

Related Information

• Wireless Support Resources
• Wireless / Mobility
• Technical Support & Documentation - Cisco Systems