iwconfig - configure a wireless network 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]
[enc E] [key K] [power P] [retry
[modu M] [commit]
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).
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.
- 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.
iwconfig eth0 essid any
iwconfig eth0 essid "My Network"
iwconfig eth0 essid -- "ANY"
- 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).
iwconfig eth0 nwid AB34
iwconfig eth0 nwid off
- 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.
iwconfig eth0 nickname "My Linux Node"
- 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.
iwconfig eth0 mode Managed
iwconfig eth0 mode Ad-Hoc
- 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 display the current frequency as a channel. Depending 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).
iwconfig eth0 freq 2422000000
iwconfig eth0 freq 2.422G
iwconfig eth0 channel 3
iwconfig eth0 channel auto
- Force the card to register to the Access Point given by the
address, 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.
iwconfig eth0 ap 00:60:1D:01:23:45
iwconfig eth0 ap any
iwconfig eth0 ap off
- 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
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.
iwconfig eth0 rate 11M
iwconfig eth0 rate auto
iwconfig eth0 rate 5.5M auto
- 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).
iwconfig eth0 txpower 15
iwconfig eth0 txpower 30mW
iwconfig eth0 txpower auto
iwconfig eth0 txpower off
- 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 hardware or a
percentage, negative values are assumed to be dBm. Depending on the
hardware implementation, this parameter may control 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/better 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 considers 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.
iwconfig eth0 sens -80
iwconfig eth0 sens 2
- 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 nothing 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 milliseconds 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).
iwconfig eth0 retry 16
iwconfig eth0 retry lifetime 300m
iwconfig eth0 retry short 12
iwconfig eth0 retry min limit 8
- 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
iwconfig eth0 rts 250
iwconfig eth0 rts off
- 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
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.
iwconfig eth0 frag 512
iwconfig eth0 frag off
- Used to manipulate encryption or scrambling keys and
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
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.
iwconfig eth0 key 0123-4567-89
iwconfig eth0 key  0123-4567-89
iwconfig eth0 key s:password 
iwconfig eth0 key 
iwconfig eth0 key open
iwconfig eth0 key off
iwconfig eth0 key restricted  0123456789
iwconfig eth0 key 01-23 key 45-67  key 
- Used to manipulate power management scheme parameters and
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).
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
- 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 independently, some may come
as a group. You may also set this parameter to auto let the
card/driver do its best.
iwconfig eth0 modu 11g
iwconfig eth0 modu CCK OFDMa
iwconfig eth0 modu auto
- 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 apply the
changes, but can be useful for debugging.
For each device which supports wireless extensions, iwconfig
the name of the MAC protocol
used (name of device for proprietary
protocols), the ESSID
(Network Name), the NWID
(or channel), the sensitivity
, the mode
operation, the Access Point
address, the bit-rate
, the RTS
, the fragmentation 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 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.
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
- 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 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
- 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
- Invalid misc
- Other packets lost in relation with specific wireless
- 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.
Jean Tourrilhes - email@example.com