iwconfig


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,
              ter/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

       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
              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
              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  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-

       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

       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
              remains  associated with the current Access Point. When the sig-
              nal 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 associ-
              ated 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
              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 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
              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

              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
              independently, some may come as a group. You may also  set  this
              parameter 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
              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  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).

       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
       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 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

       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
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