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IWCONFIG(8) Linux Programmer’s Manual IWCONFIG(8)
NAME
iwconfig - configure a wireless network interface
SYNOPSIS
iwconfig [interface]
iwconfig interface [essid X] [nwid N] [mode M] [freq F]
[channel C][sens S ][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 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 dependent. Each driver will provide
only some of them depending on hardware support, and the range of values 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 be called
Domain ID). The ESSID is used to identify cells which are part of the same
virtual network.
As opposed to the AP Address or NWID which define a single cell, the ESSID
defines a group of cells connected via repeaters or infrastructure, where
the user may roam transparently.
With some cards, you may disable the ESSID checking (ESSID promiscuous) with
off or any (and on to reenable it).
If the ESSID of your network is one of the special keywords (off, on or
any), you should use -- to escape it.
Examples :
iwconfig eth0 essid any
iwconfig eth0 essid "My Network"
iwconfig eth0 essid -- "ANY"
nwid/domain
Set the Network ID (in some products it may also be 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
belonging to the same cell.
This parameter is only used for pre-802.11 hardware, the 802.11 protocol
uses the ESSID and AP Address for this function.
With some cards, 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. A value below 1000
indicates a channel number, a value greater than 1000 is a frequency in Hz.
You may 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 iwlist(8) to
get the total number of channels, list the available frequencies, and dis-
play the current frequency as a channel. Depending on regulations, some fre-
quencies/channels may not be available.
When using Managed mode, most often the Access Point dictates the channel
and the driver may refuse the setting of the frequency. In Ad-Hoc mode, the
frequency setting may only be used at initial cell creation, and may be
ignored when joining an existing cell.
You may also use off or auto to let the card pick up the best channel (when
supported).
Examples :
iwconfig eth0 freq 2422000000
iwconfig eth0 freq 2.422G
iwconfig eth0 channel 3
iwconfig eth0 channel auto
sens Set the sensitivity threshold. This is the lowest signal level for which the
hardware will consider receive packets usable. Positive values are assumed
to be the raw value used by the hardware or a percentage, negative values
are assumed to be dBm. Depending on the hardware implementation, this param-
eter may control various functions.
This parameter may control the receive threshold, the lowest signal level
for which the hardware attempts packet reception, signals weaker than this
are ignored. This may also controls the defer threshold, the lowest signal
level for which the hardware considers the channel busy. Proper setting of
those threshold prevent the card to waste time receiving background noise.
Modern designs seems to control those thresholds automatically.
On modern cards, this parameter may control handover/roaming threshold, the
lowest signal level for which the hardware remains associated with the cur-
rent Access Point. When the signal level goes below this threshold the card
starts looking for a new/better Access Point.
Example :
iwconfig eth0 sens -80
mode Set the operating mode of the device, which depends on the network 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 acts as an
Access Point), Repeater (the node forwards packets between other wireless
nodes), Secondary (the node acts as a backup master/repeater), Monitor (the
node is not associated with any cell and passively monitor all packets on
the frequency) 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 selects the best Access Point in
range).
You may also use off to re-enable automatic mode without changing the cur-
rent Access Point, or you may use any or auto to force the card to reassoci-
ate with the currently 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. Some 802.11 products do define it,
but this is not used as far as the protocols (MAC, IP, TCP) are concerned
and completely useless as far as configuration goes. 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 various overhead.
You may append the suffix k, M or G to the value (decimal multiplier : 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 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-rates 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 increases performance in case
of hidden nodes or a large number of active nodes. This parameter sets the
size of the smallest packet for which the node sends RTS ; a value equal to
the maximum packet size disables the mechanism. You may also set this param-
eter to auto, fixed or off.
Examples :
iwconfig eth0 rts 250
iwconfig eth0 rts off
frag[mentation_threshold]
Fragmentation allows to split an IP packet in a burst of smaller fragments
transmitted on the medium. In most cases this adds overhead, but in a very
noisy environment this reduces the error penalty and allow packets to get
through interference bursts. This parameter sets the maximum fragment size ;
a value equal to the maximum packet size disables the mechanism. 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 security 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 currently active key, just enter [index] (without
entering any key value).
off and on disable and reenable encryption.
The security mode may be open or restricted, and its meaning depends on the
card used. With most cards, in open mode no authentication is used and the
card may also accept non-encrypted sessions, whereas in restricted mode only
encrypted sessions are accepted and the card will use authentication if
available.
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 precedence.
Examples :
iwconfig eth0 key 0123-4567-89
iwconfig eth0 key [3] 0123-4567-89
iwconfig eth0 key s:password [2]
iwconfig eth0 key [2]
iwconfig eth0 key 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 ups, enter period ‘value’. To set the time-
out before going back to sleep, enter timeout ‘value’. You can also add the
min and max modifiers. By default, those values are in seconds, append the
suffix m or u to specify values in milliseconds or microseconds. Sometimes,
those values are without units (number of beacon periods, dwell or similar).
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 multi-
cast 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, sets 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 abso-
lute value (without unit). To 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 in milliseconds or microseconds.
You can also add the min and max modifiers. If the card supports 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 Extensions immedi-
ately (they may wait to aggregate the changes or apply it only when the card
is brought up via ifconfig). This command (when available) forces the card
to apply all pending changes.
This is normally not needed, because the card will eventually apply the
changes, but can be useful for debugging.
DISPLAY
For each device which supports wireless extensions, iwconfig will display the name
of the MAC protocol used (name of device for proprietary protocols), the ESSID
(Network Name), the NWID, the frequency (or channel), the sensitivity, the mode of
operation, the Access Point address, the bit-rate, the RTS threshold, the fragmen-
tation threshold, the encryption key and the power management settings (depending
on availability).
The parameters displayed have the same meaning and values as the parameters you can
set, please refer to the previous part for a detailed explanation of them.
Some parameters are only displayed in short/abbreviated form (such as encryption).
You may use iwlist(8) to get all the details.
Some parameters have two modes (such as bitrate). If the value is prefixed by ‘=’,
it means that the parameter is fixed and forced to that value, if it is prefixed by
‘:’, the parameter is in automatic mode and the current value is shown (and may
change).
Access Point/Cell
An address equal to 00:00:00:00:00:00 means that the card failed to asso-
ciate with an Access Point (most likely a configuration issue). The Access
Point parameter will be shown as Cell in ad-hoc mode (for obvious reasons),
but otherwise works the same.
If /proc/net/wireless exists, iwconfig will also display its content. Note that
those values will depend on the driver and the hardware specifics, so you need to
refer to your driver documentation for proper interpretation of those values.
Link quality
Overall quality of the link. May be based on the level of contention or
interference, the bit or frame error rate, how good the received signal is,
some timing synchronisation, or other hardware metric. This is an aggregate
value, and depends totally on the driver and hardware.
Signal level
Received signal strength (RSSI - how strong the received signal is). May be
arbitrary units or dBm, iwconfig uses driver meta information to interpret
the raw value given by /proc/net/wireless and display the proper unit or
maximum value (using 8 bit arithmetic). In Ad-Hoc mode, this may be unde-
fined and you should use iwspy.
Noise level
Background noise level (when no packet is transmitted). Similar comments as
for Signal level.
Rx invalid nwid
Number of packets received with a different NWID or ESSID. Used to detect
configuration problems or adjacent network existence (on the same fre-
quency).
Rx invalid crypt
Number of packets that the hardware was unable to decrypt. This can be used
to detect invalid encryption settings.
Rx invalid frag
Number of packets for which the hardware was not able to properly re-assem-
ble the link layer fragments (most likely one was missing).
Tx excessive retries
Number of packets that the hardware failed to deliver. Most MAC protocols
will retry the packet a number of times before giving up.
Invalid misc
Other packets lost in relation with specific wireless operations.
Missed beacon
Number of periodic beacons from the Cell or the Access Point we have missed.
Beacons are sent at regular intervals to maintain the cell coordination,
failure to receive them usually indicates that the card is out of range.
AUTHOR
Jean Tourrilhes - jt AT hpl.com
FILES
/proc/net/wireless
SEE ALSO
ifconfig(8), iwspy(8), iwlist(8), iwevent(8), iwpriv(8), wireless(7).
wireless-tools 22 June 2004 IWCONFIG(8)
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