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]

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 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 networks 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, value over this is the frequency in Hz. You must 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 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 reception, 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 values 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 threshold (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), Master (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 connection 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.
    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 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 specific, usually an index in the bit-rate list. Use auto to select the 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 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 transmission 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 XXXXXXXX. To set a key other than the current key, 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 packets.
    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 parameters 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 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 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

commit
    Some cards may not apply changes done through Wireless Extensions immediately (they may wait to agregate the changes or apply it only when the card is brought up). This command (when available) force the card to apply all pending changes.
    This is normally not needed, because the card will eventually apply the changes, but can be usefull for debugging.

DISPLAY
For each device which support 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).
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 transmited).

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

invalid crypt
    Number of packets that the hardware was unable to decrypt.

invalid misc
    Other packets lost in relation with specific wireless 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).