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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