iwconfig



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 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
              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 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

       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 parameter 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. Mod-
              ern 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 current Access Point. When the  sig-
              nal  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  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   mas-
              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

       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 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

       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 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 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

       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 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 ; 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  timeout  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 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 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 absolute 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  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
       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                   22 June 2004                      IWCONFIG(8)

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