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IWCONFIG(8)                Linux Programmer's Manual               IWCONFIG(8)



NAME
       iwconfig - configure a wireless network interface

SYNOPSIS
       iwconfig [interface]
       iwconfig interface [essid X] [nwid N] [freq F] [channel C]
                          [sens S] [mode M] [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  pro-
              miscuous) with off or any (and on to reenable it).
              Examples :
                   iwconfig eth0 essid any
                   iwconfig eth0 essid "My Network"

       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.
              Examples :
                   iwconfig eth0 freq 2422000000
                   iwconfig eth0 freq 2.422G
                   iwconfig eth0 channel 3

       sens   Set  the  sensitivity threshold. This is the lowest signal level
              for which the hardware attempt packet reception, signals  weaker
              than  this  are  ignored.  This is used to avoid receiving back-
              ground noise, so you should set  it  according  to  the  average
              noise  level.  Positive  values  are assumed to be the raw value
              used by the  hardware  or  a  percentage,  negative  values  are
              assumed to be dBm.
              With  some  hardware,  this  parameter  also  controls the defer
              threshold (lowest signal level for which the  hardware  consider
              the channel busy) and the handover threshold (signal level where
              the hardware start looking for a new 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 acts as a passive monitor and
              only receives packets) 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 disable 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 disable 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, set 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).  The 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  agregate  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-
       eter  you  can  set,  please  refer to the previous part for a detailed
       explanation of them.
       Some parameters are only displayed in short/abreviated  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 - jtAThpl.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)