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]


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 wire­
       less operation (for example :  the  frequency).   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  dependant.
       Each  driver  will  provide only some of them depending on
       the hardware support, and the range of value  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 called Domain ID). The ESSID is used to
              identify  cells  which are part of the same virtual
              network.
              As opposed to the NWID which defines a single cell,
              the  ESSID  defines  a  group of cell connected via
              repeaters or infrastructure,  where  the  user  may
              roam.   With  some  card, you may disable the ESSID
              checking (ESSID promiscuous) 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 is also
              called Domain ID). As all  adjacent  wireless  net­
              works share the same medium, this parameter is used
              to differenciate  them  (create  logical  colocated
              networks) and identify nodes belonguing to the same
              cell. With some card, 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.  Value  below  1000 are the channel number,

              append the suffix k, M or G to the value (for exam­
              ple, "2.46G" for 2.46 GHz frequency), or add enough
              '0'.
              Channels  are  usually  numbered starting at 1, and
              you may use iwpriv(8) to get the  total  number  of
              channels   and   list  the  available  frequencies.
              Depending on regulations, some frequencies/channels
              may not be available.
              Examples :
                   iwconfig eth0 freq 2.422G
                   iwconfig eth0 channel 3

       sens   Set  the  sensitivity threshold. This is the lowest
              signal level for which we attempt a  packet  recep­
              tion, signal lower than this are not received. This
              is used to avoid receiving background 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 val­
              ues are assumed to be dBm.
              With some hardware, this parameter also control the
              defer  threshold  (lowest signal level for which we
              consider the channel busy) and the handover thresh­
              old  (lowest  signal level where we stay associated
              with the current access point).
              Example :
                   iwconfig eth0 sens -80

       mode   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  (network composed of many
              cells, with roaming or with an Access Point),  Mas­
              ter  (the node is the synchronisation master or act
              as an Access Point),  Repeater  (the  node  forward
              packets  on  the air), Secondary (the node act as a
              backup master/repeater) or Auto.
              Example :
                   iwconfig eth0 mode Managed

       ap     Register to the Access Point given by the  address,
              if  it is possible. When the quality of the connec­
              tion goes too low, the driver may  revert  back  to
              automatic mode.
              Example :
                   iwconfig eth0 ap 00:60:1D:01:23:45

       nick[name]
              Set  the nickname, or the station name. Most 802.11
              products do define it, but this is not used as  far
              as  the  protocols (MAC, IP, TCP) are concerned and
              completely accessory as far as configuration  goes.
              In fact only some diagnostic tools may use it.

                   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 overhead.
              You  must  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 spe­
              cific, usually an index in the bit-rate  list.  Use
              auto  to  select the automatic bit-rate mode (fall­
              back 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 lower and
              equal than this value.
              Examples :
                   iwconfig eth0 rate 11M
                   iwconfig eth0 rate auto

       rts[_threshold]
              RTS/CTS adds a handshake before each packet  trans­
              mission  to  make  sure  that the channel is clear.
              This adds overhead,  but  increase  performance  in
              case  of  hidden  nodes  or  large number of active
              nodes. This parameters set the size of the smallest
              packet  for which the node sends RTS, a value equal
              to the maximum packet size disable the scheme.  You
              may  also set this parameter to auto, fixed or off.
              Examples :
                   iwconfig eth0 rts 250
                   iwconfig eth0 rts off

       frag[mentation_threshold]
              Fragmentation allow to split a IP packet in a burst
              of  smaller fragments transmitted on the medium. In
              most cases this adds overhead, but  in  very  noisy
              environment  this  reduce  the  error penalty. This
              parameter set the maximum fragment  size,  a  value
              equal  to  the  maximum  packet  size  disable  the
              scheme. 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 encryption mode.
              To set the current encryption key, just  enter  the
              key   in   hex  digits  as  XXXX-XXXX-XXXX-XXXX  or

              append  [index]  to  the  key  itself. You can also
              enter the key as an ASCII string by  using  the  s:
              prefix.
              To change which key is the current active key, just
              enter [index] (without entering any key value).
              off and on disable and  reenable  encryption,  open
              set  the  system in open mode (accept non-encrypted
              packets) and restricted discard non-encrypted pack­
              ets.
              Examples :
                   iwconfig eth0 key 0123-4567-89
                   iwconfig eth0 key s:password [2]
                   iwconfig eth0 key [2] open
                   iwconfig eth0 key off

       power  Used  to manipulate power management scheme parame­
              ters and mode.
              To set the period between  wake  up,  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 defaults, those values
              are in seconds, append the suffix m or u to specify
              values  un milliseconds or microseconds. Sometimes,
              those values are without units (number of dwell  or
              the like).
              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  automati­
              cally 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

              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 un milliseconds or microseconds.
              You  can also add the min and max modifiers. If the
              card support 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


DISPLAY

       For each device which support wireless extensions,  iwcon­
       fig  will  display the name of the MAC protocol used (name
       of device for proprietary protocols), the  ESSID  (Network
       Name), the NWID, the frequency (or channel), the sensitiv­
       ity, 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 availability).
       See  above for explanations of what these parameters mean.
       If the label for bitrate is followed by `=', it means that
       the  parameter is fixed and forced to that value, if it is
       followed by `:' it is only the current  value  (device  in
       normal auto mode).

       If  /proc/net/wireless  exists, iwconfig will also display
       its content :

       Link quality
              Quality of the link or the modulation (what is  the
              level  of  contention  or interference, or how good
              the received signal is).

       Signal level
              Received signal strength (how strong  the  received
              signal is).

       Noise level
              Background  noise  level  (when no packet is trans­
              mited).

       invalid nwid
              Number of packets received with a  different  NWID.
              Used  to  detect configuration problems or adjacent
              network existence.

              Number of packets that the hardware was  unable  to
              decrypt.

       invalid misc
              Other  packets lost in relation with specific wire­
              less operations.


AUTHOR

       Jean Tourrilhes - jt@hpl.hp.com


FILES

       /proc/net/wireless


SEE ALSO

       ifconfig(8), iwspy(8), iwlist(8),  iwpriv(8),  wavelan(4),
       wavelan_cs(4), wvlan_cs(4), netwave_cs(4).


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