This document provides questions and answers about Aironet Linux
Technical Tips Conventions for more information on document
Where can I find the latest utilities, drivers, and firmware for my Linux
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
Downloads - Wireless Software Page.
How do I update the software for my Linux client?
A. There are three pieces to the client software:
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.
Client driver for the operating system —The client driver is the
software that manages interactions between Linux (or other operating system)
and the hardware.
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
Notes for Cisco Aironet Wireless LAN Adapters and locate the
Installation Instructions section in the Contents for information on how to
update these items.
Linux Drivers and Utilities for the Cisco Aironet 340/350 Series Client
Adapters for more information.
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.
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
When I try to compile the driver from the PCMCIA-CS directory, I get
memcpy errors. Where do I look to find the
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.
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
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.
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.
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.
Where can I find help to install my Client Card?
A. Refer to
Aironet Wireless LAN Adapters Installation and Configuration Guide for
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.
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
Problems Affecting Radio Frequency Communication for more information.
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.
Do I need special hardware to support encryption?
A. The specific hardware model of the unit determines the level of
Which devices can associate with a Client Card?
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.
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.
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.
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:
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.
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.
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.
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.