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]
[modu M] [commit]
iwconfig --help
iwconfig --version
DESCRIPTION
Iwconfig is similar to ifconfig(8), but is dedicated to the wireless in-
terfaces. 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 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 in-
frastructure, 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 Set the Network ID. As all adjacent wireless networks share the
same medium, this parameter is used to differentiate 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
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 wireless diagnostic tools may use it.
Example :
iwconfig eth0 nickname "My Linux Node"
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 acts as an Access
Point), Repeater (the node forwards packets between other wire-
less nodes), Secondary (the node acts as a backup master/re-
peater), 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
freq/channel
Set the operating frequency or channel in the device. A value be-
low 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 display the current frequency as a channel. De-
pending on regulations, some frequencies/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
ap Force the card to register to the Access Point given by the ad-
dress, if it is possible. This address is the cell identity of
the Access Point, as reported by wireless scanning, which may be
different from its network MAC address. If the wireless link is
point to point, set the address of the other end of the link. If
the link is ad-hoc, set the cell identity of the ad-hoc network.
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 current Access Point, or you may use any or auto to force the
card to reassociate with the currently best Access Point.
Example :
iwconfig eth0 ap 00:60:1D:01:23:45
iwconfig eth0 ap any
iwconfig eth0 ap off
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 multi-
plier : 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
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 au-
tomatically 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
sens Set the sensitivity threshold. This define how sensitive is the
card to poor operating conditions (low signal, interference).
Positive values are assumed to be the raw value used by the hard-
ware or a percentage, negative values are assumed to be dBm. De-
pending on the hardware implementation, this parameter may con-
trol various functions.
On modern cards, this parameter usually control handover/roaming
threshold, the lowest signal level for which the hardware remains
associated with the current Access Point. When the signal level
goes below this threshold the card starts looking for a new/bet-
ter Access Point. Some cards may use the number of missed beacons
to trigger this. For high density of Access Points, a higher
threshold make sure the card is always associated with the best
AP, for low density of APs, a lower threshold minimise the number
of failed handoffs.
On more ancient card this parameter usually controls the defer
threshold, the lowest signal level for which the hardware consid-
ers the channel busy. Signal levels above this threshold make the
hardware inhibits its own transmission whereas signals weaker
than this are ignored and the hardware is free to transmit. This
is usually strongly linked to the receive threshold, the lowest
signal level for which the hardware attempts packet reception.
Proper setting of these thresholds prevent the card to waste time
on background noise while still receiving weak transmissions.
Modern designs seems to control those thresholds automatically.
Example :
iwconfig eth0 sens -80
iwconfig eth0 sens 2
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), and the default (when noth-
ing is specified). To set the maximum length of time the MAC
should retry, enter lifetime `value'. By defaults, this value is
in seconds, append the suffix m or u to specify values in mil-
liseconds or microseconds.
You can also add the short, long, 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 short 12
iwconfig eth0 retry min limit 8
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 parameter 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 which is always
lower than the maximum packet size.
This parameter may also control Frame Bursting available on some
cards, the ability to send multiple IP packets together. This
mechanism would be enabled if the fragment size is larger than
the maximum packet size.
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 dig-
its 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 [in-
dex] (without entering any key value).
off and on disable and reenable encryption.
The security mode may be open or restricted, and its meaning de-
pends on the card used. With most cards, in open mode no authen-
tication is used and the card may also accept non-encrypted ses-
sions, whereas in restricted mode only encrypted sessions are ac-
cepted and the card will use authentication if available.
If you need to set multiple keys, or set a key and change the ac-
tive 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 timeout before going back to sleep, enter timeout `value'.
To set the generic level of power saving, enter saving `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, percentage 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 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 saving 3
iwconfig eth0 power off
iwconfig eth0 power min period 2 power max period 4
modu[lation]
Force the card to use a specific set of modulations. Modern cards
support various modulations, some which are standard, such as
802.11b or 802.11g, and some proprietary. This command force the
card to only use the specific set of modulations listed on the
command line. This can be used to fix interoperability issues.
The list of available modulations depend on the card/driver and
can be displayed using iwlist modulation. Note that some
card/driver may not be able to select each modulation listed in-
dependently, some may come as a group. You may also set this pa-
rameter to auto let the card/driver do its best.
Examples :
iwconfig eth0 modu 11g
iwconfig eth0 modu CCK OFDMa
iwconfig eth0 modu auto
commit Some cards may not apply changes done through Wireless Extensions
immediately (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 ap-
ply the changes, but can be useful for debugging.
DISPLAY
For each device which supports 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 en-
cryption key and the power management settings (depending on availabil-
ity).
The parameters displayed have the same meaning and values as the parame-
ters you can set, please refer to the previous part for a detailed ex-
planation 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 pre-
fixed 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 associate 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 con-
tention 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 in-
formation to interpret the raw value given by /proc/net/wireless
and display the proper unit or maximum value (using 8 bit arith-
metic). In Ad-Hoc mode, this may be undefined 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 frequency).
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-assemble the link layer fragments (most likely one was miss-
ing).
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@hpl.hp.com
FILES
/proc/net/wireless
SEE ALSO
ifconfig(8), iwspy(8), iwlist(8), iwevent(8), iwpriv(8), wireless(7).
wireless-tools 30 March 2006 IWCONFIG(8)
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