IWCONFIG(8)



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
       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 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  pro-
              miscuous) 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 (cre-
              ate 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 configu-
              ration 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
              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 avail-
              able frequencies, and display the current frequency as  a  chan-
              nel. 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 fre-
              quency. In Ad-Hoc mode, the frequency setting may only  be  used
              at initial cell creation, and may be ignored when joining an ex-
              isting 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  chang-
              ing  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 be-
              low 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
              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  re-
              mains  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  con-
              siders 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 trans-
              mit. 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
              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 de-
              pending 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  in-
              creases 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 maxi-
              mum 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
              digits  as  XXXX-XXXX-XXXX-XXXX or XXXXXXXX.  To set a key other
              than the current key, prepend or append [index] to the  key  it-
              self  (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
              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  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 de-
              fault, 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,  per-
              centage 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 is-
              sues.
              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  Exten-
              sions immediately (they may wait to aggregate the changes or ap-
              ply 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 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 param-
       eters 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
              information  to interpret the raw value given by /proc/net/wire-
              less 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  prop-
              erly  re-assemble  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  opera-
              tions.

       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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