HardwareComparison | LinuxDrivers | WirelessExtensions | IwConfig
Notes about iwconfig command utilitation and understanding its output
Wireless-tools: homepage
Interpreting iwconfig output
#iwconfig eth0
Cell value: Cell: 02:27:XX:XX:XX:XX the field "Access Point" or "Cell" shown by iwconfig is usefull for knowing what's happening. If it's all zeros, you are using Ad-Hoc demo mode. In IBSS Ad-Hoc mode it indicates the cell the node has joined. It should be the MAC address of the first node started and all nodes should have the same value (apart if they are out of range).
Mode Monitor: #iwconfig [eth0/wlan0/ath0] mode monitor Monitor mode is enabled with 'iwconfig [eth0/wlan0/ath0] mode monitor'. Monitor mode was added to wireless tools version 25. With later versions, you cannot use iwconfig, so please either upgrade wireless tools or use old iwpriv monitor method described below.
Previously, monitoring mode was started using iwpriv(8). This is now deprecated and it is currently implemented as a backward compatibility wrapper for iwconfig mode command. It may be removed in the future versions of the driver.
(Source: HostAP Readme file)
Wireless-tools FAQ (iwconfig, iwlist ...)
Is it allways necessary to setup a channel in a wireless configuration?
No, it depens on your configuration mode. For Ad-hoc or Master mode you should setup your channel manually but for Managed mode it is not necessary.
Managed mode clients are scanning for APs from all channels and then select one of them. At this point the channel already known from the scan results. With many cards, e.g., Prism2/2.5/3, this is implemented in the card firmware and it doesn't really matter whether you are using Windows or Linux. With cards that use host system for things like IEEE 802.11 management, e.g., Atheros ar521x-based cards, this needs to be implemented in the driver.
Long distance problems, possible solution
If you are in a area with a lot of other nodes, like using a high gain antenna for long distance communication, you may want to turn on the RTS handshaking feature. See the man page for details or simply try something like below (as root):
iwconfig wlan0 rts 64
iwconfig wlan0 frag 256
You can adjust those values, but these are small enough to see a difference when having problems. The first is a minimum packet size to use RTS on so we set that low, and the other is the max packet size to transmit, even if the actual packet is actually larger it will break the packet up. This may not always work on all drivers.
MAN PAGE
NAME
- iwconfig - configure a wireless network interface
SYNOPSIS
- iwconfig [interface] iwconfig interface [essid X] [nwid N] [freq F] [channel C]
- [sens S] [mode M] [ap A] [nick NN] [rate R] [rts RT] [frag FT] [txpower T] [enc E] [key K] [power P] [retry R] [commit]
DESCRIPTION
- Iwconfig is similar to ifconfig(8), but is dedicated to the wireless interfaces. It is used to set the parameters of the network interface which are specific to the wireless operation (for example : the frequency). Iwconfig may also be used to display those parameters, and the wireless statistics (extracted from /proc/net/wireless). All these parameters and statistics are device dependant. Each driver will provide only some of them depending on the hard ware support, and the range of value may change. Please refer to the man page of each device for details.
PARAMETERS
