IWCONFIG(8)              (30 March 2006)              IWCONFIG(8)

     NAME
          iwconfig - configure a wireless network interface

     SYNOPSIS
          iwconfig [interface]
          iwconfig interface [essid X] [nwid N
                             [channel C][sens S ]
                             [rate R] [rts RT] [frag FT
                             [enc E] [key K] [power P
                             [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 opera-
          tion (for example : the frequency).  Iwconfig may also be
          used to display those parameters, and the wireless statis-
          tics (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 net-
               work.
               As opposed to the AP Address or NWID which define a
               single cell, the ESSID defines a group of cells con-
               nected 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 key-
               words (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 dif-
               ferentiate them (create logical colocated networks) and
               identify nodes belonging to the same cell.

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               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 check-
               ing (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 com-
               pletely useless as far as configuration 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 network 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/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 available frequencies, and display the current
               frequency as a channel. 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 set-
               ting of the frequency. 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).

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               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 wire-
               less 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 with-
               out changing 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 over-
               head.
               You may append the suffix k, M or G to the value (deci-
               mal multiplier : 10^3, 10^6 and 10^9 b/s), or add
               enough '0'. Values below 1000 are card specific, usu-
               ally 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 spec-
               ify 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 automatically converted to
               dBm.

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               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 sensi-
               tive is the card to poor operating conditions (low sig-
               nal, 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 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 considers 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 transmit. 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 automati-
               cally.
               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 nothing is specified).  To set the
               maximum length of time the MAC should retry, enter
               lifetime `value'. By defaults, this value is in sec-
               onds, append the suffix m or u to specify values in

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               milliseconds or microseconds.
               You can also add the short, long, min and 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 short 12
                    iwconfig eth0 retry min limit 8

          rts[_threshold]
               RTS/CTS adds a handshake before each packet transmis-
               sion 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 maximum 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 environ-
               ment 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 avail-
               able 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

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               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'. To set the generic level of
               power saving, enter saving `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 val-
               ues are without units (number of beacon periods, dwell,
               percentage 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

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          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 pro-
               prietary. 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
               Extensions 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 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 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 availability).

          The parameters displayed have the same meaning and values as
          the parameters 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 prefixed 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

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               card failed to associate with an Access Point (most
               likely a configuration issue). The Access Point parame-
               ter 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 val-
          ues.

          Link quality
               Overall quality of the link. May be based on the level
               of contention or interference, the bit or frame error
               rate, how good the received signal is, some timing syn-
               chronisation, 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/wireless 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 adja-
               cent 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 properly 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.

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          Invalid misc
               Other packets lost in relation with specific wireless
               operations.

          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).

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