1IWCONFIG(8) Linux Programmer's Manual IWCONFIG(8)
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6 iwconfig - configure a wireless network interface
7
9 iwconfig [interface]
10 iwconfig interface [essid X] [nwid N] [mode M] [freq F]
11 [channel C][sens S ][ap A ][nick NN ]
12 [rate R] [rts RT] [frag FT] [txpower T]
13 [enc E] [key K] [power P] [retry R]
14 [commit]
15 iwconfig --help
16 iwconfig --version
17
19 Iwconfig is similar to ifconfig(8), but is dedicated to the wireless
20 interfaces. It is used to set the parameters of the network interface
21 which are specific to the wireless operation (for example : the fre‐
22 quency). Iwconfig may also be used to display those parameters, and
23 the wireless statistics (extracted from /proc/net/wireless).
24 All these parameters and statistics are device dependent. Each driver
26 will provide only some of them depending on hardware support, and the
27 range of values may change. Please refer to the man page of each device
28 for details.
29
31 essid Set the ESSID (or Network Name - in some products it may also be
32 called Domain ID). The ESSID is used to identify cells which are
33 part of the same virtual network.
34 As opposed to the AP Address or NWID which define a single cell,
35 the ESSID defines a group of cells connected via repeaters or
36 infrastructure, where the user may roam transparently.
37 With some cards, you may disable the ESSID checking (ESSID pro‐
38 miscuous) with off or any (and on to reenable it).
39 If the ESSID of your network is one of the special keywords
40 (off, on or any), you should use -- to escape it.
41 Examples :
42 iwconfig eth0 essid any
43 iwconfig eth0 essid "My Network"
44 iwconfig eth0 essid -- "ANY"
45 nwid/domain
47 Set the Network ID (in some products it may also be called
48 Domain ID). As all adjacent wireless networks share the same
49 medium, this parameter is used to differenciate them (create
50 logical colocated networks) and identify nodes belonging to the
51 same cell.
52 This parameter is only used for pre-802.11 hardware, the 802.11
53 protocol uses the ESSID and AP Address for this function.
54 With some cards, you may disable the Network ID checking (NWID
55 promiscuous) with off (and on to reenable it).
56 Examples :
57 iwconfig eth0 nwid AB34
58 iwconfig eth0 nwid off
59 nick[name]
61 Set the nickname, or the station name. Some 802.11 products do
62 define it, but this is not used as far as the protocols (MAC,
63 IP, TCP) are concerned and completely useless as far as configu‐
64 ration goes. Only some wireless diagnostic tools may use it.
65 Example :
66 iwconfig eth0 nickname "My Linux Node"
67 mode Set the operating mode of the device, which depends on the net‐
69 work topology. The mode can be Ad-Hoc (network composed of only
70 one cell and without Access Point), Managed (node connects to a
71 network composed of many Access Points, with roaming), Master
72 (the node is the synchronisation master or acts as an Access
73 Point), Repeater (the node forwards packets between other wire‐
74 less nodes), Secondary (the node acts as a backup mas‐
75 ter/repeater), Monitor (the node is not associated with any cell
76 and passively monitor all packets on the frequency) or Auto.
77 Example :
78 iwconfig eth0 mode Managed
79 iwconfig eth0 mode Ad-Hoc
80 freq/channel
82 Set the operating frequency or channel in the device. A value
83 below 1000 indicates a channel number, a value greater than 1000
84 is a frequency in Hz. You may append the suffix k, M or G to the
85 value (for example, "2.46G" for 2.46 GHz frequency), or add
86 enough '0'.
87 Channels are usually numbered starting at 1, and you may use
88 iwlist(8) to get the total number of channels, list the avail‐
89 able frequencies, and display the current frequency as a chan‐
90 nel. Depending on regulations, some frequencies/channels may not
91 be available.
92 When using Managed mode, most often the Access Point dictates
93 the channel and the driver may refuse the setting of the fre‐
94 quency. In Ad-Hoc mode, the frequency setting may only be used
95 at initial cell creation, and may be ignored when joining an
96 existing cell.
97 You may also use off or auto to let the card pick up the best
98 channel (when supported).
99 Examples :
100 iwconfig eth0 freq 2422000000
101 iwconfig eth0 freq 2.422G
102 iwconfig eth0 channel 3
103 iwconfig eth0 channel auto
104 ap Force the card to register to the Access Point given by the
106 address, if it is possible. This address is the cell identity of
107 the Access Point, as reported by wireless scanning, which may be
108 different from its network MAC address. If the wireless link is
109 point to point, set the address of the other end of the link. If
110 the link is ad-hoc, set the cell identity of the ad-hoc network.
111 When the quality of the connection goes too low, the driver may
112 revert back to automatic mode (the card selects the best Access
113 Point in range).
114 You may also use off to re-enable automatic mode without chang‐
115 ing the current Access Point, or you may use any or auto to
116 force the card to reassociate with the currently best Access
117 Point.
118 Example :
119 iwconfig eth0 ap 00:60:1D:01:23:45
120 iwconfig eth0 ap any
121 iwconfig eth0 ap off
122 rate/bit[rate]
124 For cards supporting multiple bit rates, set the bit-rate in
125 b/s. The bit-rate is the speed at which bits are transmitted
126 over the medium, the user speed of the link is lower due to
127 medium sharing and various overhead.
128 You may append the suffix k, M or G to the value (decimal multi‐
129 plier : 10^3, 10^6 and 10^9 b/s), or add enough '0'. Values
130 below 1000 are card specific, usually an index in the bit-rate
131 list. Use auto to select automatic bit-rate mode (fallback to
132 lower rate on noisy channels), which is the default for most
133 cards, and fixed to revert back to fixed setting. If you specify
134 a bit-rate value and append auto, the driver will use all bit-
135 rates lower and equal than this value.
136 Examples :
137 iwconfig eth0 rate 11M
138 iwconfig eth0 rate auto
139 iwconfig eth0 rate 5.5M auto
140 txpower
142 For cards supporting multiple transmit powers, sets the transmit
143 power in dBm. If W is the power in Watt, the power in dBm is P =
144 30 + 10.log(W). If the value is postfixed by mW, it will be
145 automatically converted to dBm.
146 In addition, on and off enable and disable the radio, and auto
147 and fixed enable and disable power control (if those features
148 are available).
149 Examples :
150 iwconfig eth0 txpower 15
151 iwconfig eth0 txpower 30mW
152 iwconfig eth0 txpower auto
153 iwconfig eth0 txpower off
154 sens Set the sensitivity threshold. This define how sensitive is the
156 card to poor operating conditions (low signal, interference).
157 Positive values are assumed to be the raw value used by the
158 hardware or a percentage, negative values are assumed to be dBm.
159 Depending on the hardware implementation, this parameter may
160 control various functions.
161 On modern cards, this parameter usually control handover/roaming
162 threshold, the lowest signal level for which the hardware
163 remains associated with the current Access Point. When the sig‐
164 nal level goes below this threshold the card starts looking for
165 a new/better Access Point. Some cards may use the number of
166 missed beacons to trigger this. For high density of Access
167 Points, a higher threshold make sure the card is always associ‐
168 ated with the best AP, for low density of APs, a lower threshold
169 minimise the number of failed handoffs.
170 On more ancient card this parameter usually controls the defer
171 threshold, the lowest signal level for which the hardware con‐
172 siders the channel busy. Signal levels above this threshold make
173 the hardware inhibits its own transmission whereas signals
174 weaker than this are ignored and the hardware is free to trans‐
175 mit. This is usually strongly linked to the receive threshold,
176 the lowest signal level for which the hardware attempts packet
177 reception. Proper setting of these thresholds prevent the card
178 to waste time on background noise while still receiving weak
179 transmissions. Modern designs seems to control those thresholds
180 automatically.
181 Example :
182 iwconfig eth0 sens -80
183 iwconfig eth0 sens 2
184 retry Most cards have MAC retransmissions, and some allow to set the
186 behaviour of the retry mechanism.
187 To set the maximum number of retries, enter limit `value'. This
188 is an absolute value (without unit). To set the maximum length
189 of time the MAC should retry, enter lifetime `value'. By
190 defaults, this value in in seconds, append the suffix m or u to
191 specify values in milliseconds or microseconds.
192 You can also add the min and max modifiers. If the card supports
193 automatic mode, they define the bounds of the limit or lifetime.
194 Some other cards define different values depending on packet
195 size, for example in 802.11 min limit is the short retry limit
196 (non RTS/CTS packets).
197 Examples :
198 iwconfig eth0 retry 16
199 iwconfig eth0 retry lifetime 300m
200 iwconfig eth0 retry min limit 8
201 rts[_threshold]
203 RTS/CTS adds a handshake before each packet transmission to make
204 sure that the channel is clear. This adds overhead, but
205 increases performance in case of hidden nodes or a large number
206 of active nodes. This parameter sets the size of the smallest
207 packet for which the node sends RTS ; a value equal to the maxi‐
208 mum packet size disables the mechanism. You may also set this
209 parameter to auto, fixed or off.
210 Examples :
211 iwconfig eth0 rts 250
212 iwconfig eth0 rts off
213 frag[mentation_threshold]
215 Fragmentation allows to split an IP packet in a burst of smaller
216 fragments transmitted on the medium. In most cases this adds
217 overhead, but in a very noisy environment this reduces the error
218 penalty and allow packets to get through interference bursts.
219 This parameter sets the maximum fragment size which is always
220 lower than the maximum packet size.
221 This parameter may also control Frame Bursting available on some
222 cards, the ability to send multiple IP packets together. This
223 mechanism would be enabled if the fragment size is larger than
224 the maximum packet size.
225 You may also set this parameter to auto, fixed or off.
226 Examples :
227 iwconfig eth0 frag 512
228 iwconfig eth0 frag off
229 key/enc[ryption]
231 Used to manipulate encryption or scrambling keys and security
232 mode.
233 To set the current encryption key, just enter the key in hex
234 digits as XXXX-XXXX-XXXX-XXXX or XXXXXXXX. To set a key other
235 than the current key, prepend or append [index] to the key
236 itself (this won't change which is the active key). You can also
237 enter the key as an ASCII string by using the s: prefix.
238 Passphrase is currently not supported.
239 To change which key is the currently active key, just enter
240 [index] (without entering any key value).
241 off and on disable and reenable encryption.
242 The security mode may be open or restricted, and its meaning
243 depends on the card used. With most cards, in open mode no
244 authentication is used and the card may also accept non-
245 encrypted sessions, whereas in restricted mode only encrypted
246 sessions are accepted and the card will use authentication if
247 available.
248 If you need to set multiple keys, or set a key and change the
249 active key, you need to use multiple key directives. Arguments
250 can be put in any order, the last one will take precedence.
251 Examples :
252 iwconfig eth0 key 0123-4567-89
253 iwconfig eth0 key [3] 0123-4567-89
254 iwconfig eth0 key s:password [2]
255 iwconfig eth0 key [2]
256 iwconfig eth0 key open
257 iwconfig eth0 key off
258 iwconfig eth0 key restricted [3] 0123456789
259 iwconfig eth0 key 01-23 key 45-67 [4] key [4]
260 power Used to manipulate power management scheme parameters and mode.
262 To set the period between wake ups, enter period `value'. To
263 set the timeout before going back to sleep, enter timeout
264 `value'. You can also add the min and max modifiers. By
265 default, those values are in seconds, append the suffix m or u
266 to specify values in milliseconds or microseconds. Sometimes,
267 those values are without units (number of beacon periods, dwell
268 or similar).
269 off and on disable and reenable power management. Finally, you
270 may set the power management mode to all (receive all packets),
271 unicast (receive unicast packets only, discard multicast and
272 broadcast) and multicast (receive multicast and broadcast only,
273 discard unicast packets).
274 Examples :
275 iwconfig eth0 power period 2
276 iwconfig eth0 power 500m unicast
277 iwconfig eth0 power timeout 300u all
278 iwconfig eth0 power off
279 iwconfig eth0 power min period 2 power max period 4
280 commit Some cards may not apply changes done through Wireless Exten‐
282 sions immediately (they may wait to aggregate the changes or
283 apply it only when the card is brought up via ifconfig). This
284 command (when available) forces the card to apply all pending
285 changes.
286 This is normally not needed, because the card will eventually
287 apply the changes, but can be useful for debugging.
288
290 For each device which supports wireless extensions, iwconfig will dis‐
291 play the name of the MAC protocol used (name of device for proprietary
292 protocols), the ESSID (Network Name), the NWID, the frequency (or chan‐
293 nel), the sensitivity, the mode of operation, the Access Point address,
294 the bit-rate, the RTS threshold, the fragmentation threshold, the
295 encryption key and the power management settings (depending on avail‐
296 ability).
297 The parameters displayed have the same meaning and values as the param‐
299 eters you can set, please refer to the previous part for a detailed
300 explanation of them.
301 Some parameters are only displayed in short/abbreviated form (such as
302 encryption). You may use iwlist(8) to get all the details.
303 Some parameters have two modes (such as bitrate). If the value is pre‐
304 fixed by `=', it means that the parameter is fixed and forced to that
305 value, if it is prefixed by `:', the parameter is in automatic mode and
306 the current value is shown (and may change).
307 Access Point/Cell
309 An address equal to 00:00:00:00:00:00 means that the card failed
310 to associate with an Access Point (most likely a configuration
311 issue). The Access Point parameter will be shown as Cell in ad-
312 hoc mode (for obvious reasons), but otherwise works the same.
313 If /proc/net/wireless exists, iwconfig will also display its content.
315 Note that those values will depend on the driver and the hardware
316 specifics, so you need to refer to your driver documentation for proper
317 interpretation of those values.
318 Link quality
320 Overall quality of the link. May be based on the level of con‐
321 tention or interference, the bit or frame error rate, how good
322 the received signal is, some timing synchronisation, or other
323 hardware metric. This is an aggregate value, and depends totally
324 on the driver and hardware.
325 Signal level
327 Received signal strength (RSSI - how strong the received signal
328 is). May be arbitrary units or dBm, iwconfig uses driver meta
329 information to interpret the raw value given by /proc/net/wire‐
330 less and display the proper unit or maximum value (using 8 bit
331 arithmetic). In Ad-Hoc mode, this may be undefined and you
332 should use iwspy.
333 Noise level
335 Background noise level (when no packet is transmitted). Similar
336 comments as for Signal level.
337 Rx invalid nwid
339 Number of packets received with a different NWID or ESSID. Used
340 to detect configuration problems or adjacent network existence
341 (on the same frequency).
342 Rx invalid crypt
344 Number of packets that the hardware was unable to decrypt. This
345 can be used to detect invalid encryption settings.
346 Rx invalid frag
348 Number of packets for which the hardware was not able to prop‐
349 erly re-assemble the link layer fragments (most likely one was
350 missing).
351 Tx excessive retries
353 Number of packets that the hardware failed to deliver. Most MAC
354 protocols will retry the packet a number of times before giving
355 up.
356 Invalid misc
358 Other packets lost in relation with specific wireless opera‐
359 tions.
360 Missed beacon
362 Number of periodic beacons from the Cell or the Access Point we
363 have missed. Beacons are sent at regular intervals to maintain
364 the cell coordination, failure to receive them usually indicates
365 that the card is out of range.
366
368 Jean Tourrilhes - jt@hpl.hp.com
369
371 /proc/net/wireless
372
374 ifconfig(8), iwspy(8), iwlist(8), iwevent(8), iwpriv(8), wireless(7).
375wireless-tools 09 March 2006 IWCONFIG(8)