iwconfig
IWCONFIG(8) Linux Programmer's Manual IWCONFIG(8)
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]
iwconfig --help
iwconfig --version
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 fre-
quency). 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 hardware support, and
the range of value may change. Please refer to the man page of each
device for details.
PARAMETERS
essid Set the ESSID (or Network Name - in some products it may also
called Domain ID). The ESSID is used to identify cells which are
part of the same virtual network.
As opposed to the NWID which defines a single cell, the ESSID
defines a group of cell connected via repeaters or infrastruc-
ture, where the user may roam. With some card, you may disable
the ESSID checking (ESSID promiscuous) with off or any (and on
to reenable it).
Examples :
iwconfig eth0 essid any
iwconfig eth0 essid "My Network"
nwid/domain
Set the Network ID (in some products it is also called Domain
ID). As all adjacent wireless networks share the same medium,
this parameter is used to differenciate them (create logical
colocated networks) and identify nodes belonguing to the same
cell. With some card, you may disable the Network ID checking
(NWID promiscuous) with off (and on to reenable it).
Examples :
iwconfig eth0 nwid AB34
iwconfig eth0 nwid off
freq/channel
Set the operating frequency or channel in the device. Value
below 1000 are the channel number, value over this is the fre-
quency in Hz. You must append the suffix k, M or G to the value
(for example, "2.46G" for 2.46 GHz frequency), or add enough
'0'.
Channels are usually numbered starting at 1, and you may use
iwpriv(8) to get the total number of channels and list the
available frequencies. Depending on regulations, some frequen-
cies/channels may not be available.
Examples :
iwconfig eth0 freq 2.422G
iwconfig eth0 channel 3
sens Set the sensitivity threshold. This is the lowest signal level
for which we attempt a packet reception, signal lower than this
are not received. This is used to avoid receiving background
noise, so you should set it according to the average noise
level. Positive values are assumed to be the raw value used by
the hardware or a percentage, negative values are assumed to be
dBm.
With some hardware, this parameter also control the defer
threshold (lowest signal level for which we consider the channel
busy) and the handover threshold (lowest signal level where we
stay associated with the current access point).
Example :
iwconfig eth0 sens -80
mode Set the operating mode of the device, which depends on the net-
work topology. The mode can be Ad-hoc (network composed of only
one cell and without Access Point), Managed (node connects to a
network composed of many Access Points, with roaming), Master
(the node is the synchronisation master or act as an Access
Point), Repeater (the node forward packets between other wire-
less nodes), Secondary (the node act as a backup mas-
ter/repeater), Monitor (the node act as a passive monitor and
only receives packets) or Auto.
Example :
iwconfig eth0 mode Managed
iwconfig eth0 mode Ad-Hoc
ap Force the card to register to the Access Point given by the
address, if it is possible. When the quality of the connection
goes too low, the driver may revert back to automatic mode (the
card finds the best Access Point in range).
You may also use off to re-enable automatic mode without chang-
ing the current Access Point, or you may use any or auto to
force the card to reassociate with the current best Access
Point.
Example :
iwconfig eth0 ap 00:60:1D:01:23:45
iwconfig eth0 ap any
iwconfig eth0 ap off
nick[name]
Set the nickname, or the station name. Most 802.11 products do
define it, but this is not used as far as the protocols (MAC,
IP, TCP) are concerned and completely accessory as far as con-
figuration goes. In fact only some diagnostic tools may use it.
Example :
iwconfig eth0 nickname "My Linux Node"
rate/bit[rate]
For cards supporting multiple bit rates, set the bit-rate in
b/s. The bit-rate is the speed at which bits are transmitted
over the medium, the user speed of the link is lower due to
medium sharing and overhead.
You must append the suffix k, M or G to the value (decimal mul-
tiplier : 10^3, 10^6 and 10^9 b/s), or add enough '0'. Values
below 1000 are card specific, usually an index in the bit-rate
list. Use auto to select the automatic bit-rate mode (fallback
to lower rate on noisy channels), which is the default for most
cards, and fixed to revert back to fixed setting. If you specify
a bit-rate value and append auto, the driver will use all bit
lower and equal than this value.
Examples :
iwconfig eth0 rate 11M
iwconfig eth0 rate auto
iwconfig eth0 rate 5.5M auto
rts[_threshold]
RTS/CTS adds a handshake before each packet transmission to make
sure that the channel is clear. This adds overhead, but increase
performance in case of hidden nodes or large number of active
nodes. This parameters set the size of the smallest packet for
which the node sends RTS, a value equal to the maximum packet
size disable the scheme. You may also set this parameter to
auto, fixed or off.
Examples :
iwconfig eth0 rts 250
iwconfig eth0 rts off
frag[mentation_threshold]
Fragmentation allow to split a IP packet in a burst of smaller
fragments transmitted on the medium. In most cases this adds
overhead, but in very noisy environment this reduce the error
penalty. This parameter set the maximum fragment size, a value
equal to the maximum packet size disable the scheme. You may
also set this parameter to auto, fixed or off.
Examples :
iwconfig eth0 frag 512
iwconfig eth0 frag off
key/enc[ryption]
Used to manipulate encryption or scrambling keys and encryption
mode.
To set the current encryption key, just enter the key in hex
digits as XXXX-XXXX-XXXX-XXXX or XXXXXXXX. To set a key other
than the current key, prepend or append [index] to the key
itself (this won't change which is the active key). You can also
enter the key as an ASCII string by using the s: prefix.
Passphrase is currently not supported.
To change which key is the current active key, just enter
[index] (without entering any key value).
off and on disable and reenable encryption, open set the system
in open mode (accept non-encrypted packets) and restricted dis-
card non-encrypted packets.
If you need to set multiple keys, or set a key and change the
active key, you need to use multiple key directives. Arguments
can be put in any order, the last one will take precendence.
Examples :
iwconfig eth0 key 0123-4567-89
iwconfig eth0 key s:password [2]
iwconfig eth0 key [2] open
iwconfig eth0 key off
iwconfig eth0 key restricted [3] 0123456789
iwconfig eth0 key 01-23 key 45-67 [4] key [4]
power Used to manipulate power management scheme parameters and mode.
To set the period between wake up, enter period `value'. To set
the timeout before going back to sleep, enter timeout `value'.
You can also add the min and max modifiers. By defaults, those
values are in seconds, append the suffix m or u to specify val-
ues un milliseconds or microseconds. Sometimes, those values are
without units (number of dwell or the like).
off and on disable and reenable power management. Finally, you
may set the power management mode to all (receive all packets),
unicast (receive unicast packets only, discard multicast and
broadcast) and multicast (receive multicast and broadcast only,
discard unicast packets).
Examples :
iwconfig eth0 power period 2
iwconfig eth0 power 500m unicast
iwconfig eth0 power timeout 300u all
iwconfig eth0 power off
iwconfig eth0 power min period 2 power max period 4
txpower
For cards supporting multiple transmit powers, set the transmit
power in dBm. If W is the power in Watt, the power in dBm is P =
30 + 10.log(W). If the value is postfixed by mW, it will be
automatically converted to dBm.
In addition, on and off enable and disable the radio, and auto
and fixed enable and disable power control (if those features
are available).
Examples :
iwconfig eth0 txpower 15
iwconfig eth0 txpower 30mW
iwconfig eth0 txpower auto
iwconfig eth0 txpower off
retry Most cards have MAC retransmissions, and some allow to set the
behaviour of the retry mechanism.
To set the maximum number of retries, enter limit `value'. This
is an absolute value (without unit). The set the maximum length
of time the MAC should retry, enter lifetime `value'. By
defaults, this value in in seconds, append the suffix m or u to
specify values un milliseconds or microseconds.
You can also add the min and max modifiers. If the card support
automatic mode, they define the bounds of the limit or lifetime.
Some other cards define different values depending on packet
size, for example in 802.11 min limit is the short retry limit
(non RTS/CTS packets).
Examples :
iwconfig eth0 retry 16
iwconfig eth0 retry lifetime 300m
iwconfig eth0 retry min limit 8
commit Some cards may not apply changes done through Wireless Exten-
sions immediately (they may wait to agregate the changes or
apply it only when the card is brought up via ifconfig). This
command (when available) force the card to apply all pending
changes.
This is normally not needed, because the card will eventually
apply the changes, but can be usefull for debugging.
DISPLAY
For each device which support wireless extensions, iwconfig will dis-
play the name of the MAC protocol used (name of device for proprietary
protocols), the ESSID (Network Name), the NWID, the frequency (or chan-
nel), the sensitivity, the mode of operation, the Access Point address,
the bit-rate the RTS threshold, the fragmentation threshold, the
encryption key and the power management settings (depending on avail-
ability).
See above for explanations of what these parameters mean.
If the label for bitrate is followed by `=', it means that the parame-
ter is fixed and forced to that value, if it is followed by `:' it is
only the current value (device in normal auto mode).
If /proc/net/wireless exists, iwconfig will also display its content :
Link quality
Quality of the link or the modulation (what is the level of con-
tention or interference, or how good the received signal is).
Signal level
Received signal strength (how strong the received signal is).
Noise level
Background noise level (when no packet is transmited).
invalid nwid
Number of packets received with a different NWID. Used to detect
configuration problems or adjacent network existence.
invalid crypt
Number of packets that the hardware was unable to decrypt.
invalid misc
Other packets lost in relation with specific wireless opera-
tions.
AUTHOR
Jean Tourrilhes - jt@hpl.hp.com
FILES
/proc/net/wireless
SEE ALSO
ifconfig(8), iwspy(8), iwlist(8), iwpriv(8), wavelan(4), wavelan_cs(4),
wvlan_cs(4), netwave_cs(4).
net-tools 31 October 1996 IWCONFIG(8)
