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1 office 1 .\" Jean II - HPLB - 1996 => HPL - 2004
2 .\" iwconfig.8
3 .\"
4 .TH IWCONFIG 8 "30 March 2006" "wireless-tools" "Linux Programmer's Manual"
5 .\"
6 .\" NAME part
7 .\"
8 .SH NAME
9 iwconfig \- configure a wireless network interface
10 .\"
11 .\" SYNOPSIS part
12 .\"
13 .SH SYNOPSIS
14 .BI "iwconfig [" interface ]
15 .br
16 .BI "iwconfig " interface " [essid " X "] [nwid " N "] [mode " M "] [freq " F "]
17 .br
18 .BI " [channel " C ] [sens " S "] [ap " A "] [nick " NN ]
19 .br
20 .BI " [rate " R "] [rts " RT "] [frag " FT "] [txpower " T ]
21 .br
22 .BI " [enc " E "] [key " K "] [power " P "] [retry " R ]
23 .br
24 .BI " [modu " M "] [commit]
25 .br
26 .BI "iwconfig --help"
27 .br
28 .BI "iwconfig --version"
29 .\"
30 .\" DESCRIPTION part
31 .\"
32 .SH DESCRIPTION
33 .B Iwconfig
34 is similar to
35 .IR ifconfig (8),
36 but is dedicated to the wireless interfaces. It is used to set the
37 parameters of the network interface which are specific to the wireless
38 operation (for example : the frequency).
39 .B Iwconfig
40 may also be used to display those parameters, and the wireless
41 statistics (extracted from
42 .IR /proc/net/wireless ).
43 .PP
44 All these parameters and statistics are device dependent. Each driver
45 will provide only some of them depending on hardware support, and the
46 range of values may change. Please refer to the man page of each
47 device for details.
48 .\"
49 .\" PARAMETER part
50 .\"
51 .SH PARAMETERS
52 .TP
53 .B essid
54 Set the ESSID (or Network Name - in some products it may also be
55 called Domain ID). The ESSID is used to identify cells which are part
56 of the same virtual network.
57 .br
58 As opposed to the AP Address or NWID which define a single cell, the
59 ESSID defines a group of cells connected via repeaters or
60 infrastructure, where the user may roam transparently.
61 .br
62 With some cards, you may disable the ESSID checking (ESSID
63 promiscuous) with
64 .IR off " or " any " (and " on
65 to reenable it).
66 .br
67 If the ESSID of your network is one of the special keywords
68 .RI ( off ", " on " or " any ),
69 you should use
70 .I --
71 to escape it.
72 .br
73 .B Examples :
74 .br
75 .I " iwconfig eth0 essid any"
76 .br
77 .I " iwconfig eth0 essid ""My Network""
78 .br
79 .I " iwconfig eth0 essid -- ""ANY""
80 .TP
81 .BR nwid
82 Set the Network ID. As all adjacent wireless networks share the same
83 medium, this parameter is used to differentiate them (create logical
84 colocated networks) and identify nodes belonging to the same cell.
85 .br
86 This parameter is only used for pre-802.11 hardware, the 802.11
87 protocol uses the ESSID and AP Address for this function.
88 .br
89 With some cards, you may disable the Network ID checking (NWID
90 promiscuous) with
91 .IR off " (and " on
92 to reenable it).
93 .br
94 .B Examples :
95 .br
96 .I " iwconfig eth0 nwid AB34
97 .br
98 .I " iwconfig eth0 nwid off"
99 .TP
100 .BR nick [name]
101 Set the nickname, or the station name. Some 802.11 products do define
102 it, but this is not used as far as the protocols (MAC, IP, TCP) are
103 concerned and completely useless as far as configuration goes. Only
104 some wireless diagnostic tools may use it.
105 .br
106 .B Example :
107 .br
108 .I " iwconfig eth0 nickname ""My Linux Node""
109 .TP
110 .B mode
111 Set the operating mode of the device, which depends on the network
112 topology. The mode can be
113 .I Ad-Hoc
114 (network composed of only one cell and without Access Point),
115 .I Managed
116 (node connects to a network composed of many Access Points, with roaming),
117 .I Master
118 (the node is the synchronisation master or acts as an Access Point),
119 .I Repeater
120 (the node forwards packets between other wireless nodes),
121 .I Secondary
122 (the node acts as a backup master/repeater),
123 .I Monitor
124 (the node is not associated with any cell and passively monitor all
125 packets on the frequency) or
126 .IR Auto .
127 .br
128 .B Example :
129 .br
130 .I " iwconfig eth0 mode Managed"
131 .br
132 .I " iwconfig eth0 mode Ad-Hoc"
133 .TP
134 .BR freq / channel
135 Set the operating frequency or channel in the device. A value below
136 1000 indicates a channel number, a value greater than 1000 is a
137 frequency in Hz. You may append the suffix k, M or G to the value (for
138 example, "2.46G" for 2.46 GHz frequency), or add enough '0'.
139 .br
140 Channels are usually numbered starting at 1, and you may use
141 .IR iwlist (8)
142 to get the total number of channels, list the available frequencies,
143 and display the current frequency as a channel. Depending on
144 regulations, some frequencies/channels may not be available.
145 .br
146 When using Managed mode, most often the Access Point dictates the
147 channel and the driver may refuse the setting of the frequency. In
148 Ad-Hoc mode, the frequency setting may only be used at initial cell
149 creation, and may be ignored when joining an existing cell.
150 .br
151 You may also use
152 .I off
153 or
154 .I auto
155 to let the card pick up the best channel (when supported).
156 .br
157 .B Examples :
158 .br
159 .I " iwconfig eth0 freq 2422000000"
160 .br
161 .I " iwconfig eth0 freq 2.422G"
162 .br
163 .I " iwconfig eth0 channel 3"
164 .br
165 .I " iwconfig eth0 channel auto"
166 .TP
167 .B ap
168 Force the card to register to the Access Point given by the address,
169 if it is possible. This address is the cell identity of the Access
170 Point, as reported by wireless scanning, which may be different from
171 its network MAC address. If the wireless link is point to point, set
172 the address of the other end of the link. If the link is ad-hoc, set
173 the cell identity of the ad-hoc network.
174 .br
175 When the quality of the connection goes too low, the driver may revert
176 back to automatic mode (the card selects the best Access Point in
177 range).
178 .br
179 You may also use
180 .I off
181 to re-enable automatic mode without changing the current Access Point,
182 or you may use
183 .I any
184 or
185 .I auto
186 to force the card to reassociate with the currently best Access Point.
187 .br
188 .B Example :
189 .br
190 .I " iwconfig eth0 ap 00:60:1D:01:23:45"
191 .br
192 .I " iwconfig eth0 ap any"
193 .br
194 .I " iwconfig eth0 ap off"
195 .TP
196 .BR rate / bit [rate]
197 For cards supporting multiple bit rates, set the bit-rate in b/s. The
198 bit-rate is the speed at which bits are transmitted over the medium,
199 the user speed of the link is lower due to medium sharing and
200 various overhead.
201 .br
202 You may append the suffix k, M or G to the value (decimal multiplier :
203 10^3, 10^6 and 10^9 b/s), or add enough '0'. Values below 1000 are
204 card specific, usually an index in the bit-rate list. Use
205 .I auto
206 to select automatic bit-rate mode (fallback to lower rate on noisy
207 channels), which is the default for most cards, and
208 .I fixed
209 to revert back to fixed setting. If you specify a bit-rate value and append
210 .IR auto ,
211 the driver will use all bit-rates lower and equal than this value.
212 .br
213 .B Examples :
214 .br
215 .I " iwconfig eth0 rate 11M"
216 .br
217 .I " iwconfig eth0 rate auto"
218 .br
219 .I " iwconfig eth0 rate 5.5M auto"
220 .TP
221 .BR txpower
222 For cards supporting multiple transmit powers, sets the transmit power
223 in dBm. If
224 .I W
225 is the power in Watt, the power in dBm is
226 .IR "P = 30 + 10.log(W)" .
227 If the value is postfixed by
228 .IR mW ,
229 it will be automatically converted to dBm.
230 .br
231 In addition,
232 .IR on " and " off
233 enable and disable the radio, and
234 .IR auto " and " fixed
235 enable and disable power control (if those features are available).
236 .br
237 .B Examples :
238 .br
239 .I " iwconfig eth0 txpower 15"
240 .br
241 .I " iwconfig eth0 txpower 30mW"
242 .br
243 .I " iwconfig eth0 txpower auto"
244 .br
245 .I " iwconfig eth0 txpower off"
246 .TP
247 .B sens
248 Set the sensitivity threshold. This define how sensitive is the card
249 to poor operating conditions (low signal, interference). Positive
250 values are assumed to be the raw value used by the hardware or a
251 percentage, negative values are assumed to be dBm. Depending on the
252 hardware implementation, this parameter may control various functions.
253 .br
254 On modern cards, this parameter usually control handover/roaming
255 threshold, the lowest signal level for which the hardware remains
256 associated with the current Access Point. When the signal level goes
257 below this threshold the card starts looking for a new/better Access
258 Point. Some cards may use the number of missed beacons to trigger
259 this. For high density of Access Points, a higher threshold make sure
260 the card is always associated with the best AP, for low density of
261 APs, a lower threshold minimise the number of failed handoffs.
262 .br
263 On more ancient card this parameter usually controls the defer
264 threshold, the lowest signal level for which the hardware considers
265 the channel busy. Signal levels above this threshold make the hardware
266 inhibits its own transmission whereas signals weaker than this are
267 ignored and the hardware is free to transmit. This is usually strongly
268 linked to the receive threshold, the lowest signal level for which the
269 hardware attempts packet reception. Proper setting of these thresholds
270 prevent the card to waste time on background noise while still
271 receiving weak transmissions. Modern designs seems to control those
272 thresholds automatically.
273 .br
274 .br
275 .B Example :
276 .br
277 .I " iwconfig eth0 sens -80"
278 .br
279 .I " iwconfig eth0 sens 2"
280 .TP
281 .BR retry
282 Most cards have MAC retransmissions, and some allow to set the
283 behaviour of the retry mechanism.
284 .br
285 To set the maximum number of retries, enter
286 .IR "limit `value'" .
287 This is an absolute value (without unit), and the default (when
288 nothing is specified).
289 To set the maximum length of time the MAC should retry, enter
290 .IR "lifetime `value'" .
291 By defaults, this value in in seconds, append the suffix m or u to
292 specify values in milliseconds or microseconds.
293 .br
294 You can also add the
295 .IR short ", " long ", " min " and " max
296 modifiers. If the card supports automatic mode, they define the bounds
297 of the limit or lifetime. Some other cards define different values
298 depending on packet size, for example in 802.11
299 .I min limit
300 is the short retry limit (non RTS/CTS packets).
301 .br
302 .B Examples :
303 .br
304 .I " iwconfig eth0 retry 16"
305 .br
306 .I " iwconfig eth0 retry lifetime 300m"
307 .br
308 .I " iwconfig eth0 retry short 12"
309 .br
310 .I " iwconfig eth0 retry min limit 8"
311 .TP
312 .BR rts [_threshold]
313 RTS/CTS adds a handshake before each packet transmission to make sure
314 that the channel is clear. This adds overhead, but increases
315 performance in case of hidden nodes or a large number of active
316 nodes. This parameter sets the size of the smallest packet for which
317 the node sends RTS ; a value equal to the maximum packet size disables
318 the mechanism. You may also set this parameter to
319 .IR auto ", " fixed " or " off .
320 .br
321 .B Examples :
322 .br
323 .I " iwconfig eth0 rts 250"
324 .br
325 .I " iwconfig eth0 rts off"
326 .TP
327 .BR frag [mentation_threshold]
328 Fragmentation allows to split an IP packet in a burst of smaller
329 fragments transmitted on the medium. In most cases this adds overhead,
330 but in a very noisy environment this reduces the error penalty and
331 allow packets to get through interference bursts. This parameter sets
332 the maximum fragment size which is always lower than the maximum
333 packet size.
334 .br
335 This parameter may also control Frame Bursting available on some
336 cards, the ability to send multiple IP packets together. This
337 mechanism would be enabled if the fragment size is larger than the
338 maximum packet size.
339 .br
340 You may also set this parameter to
341 .IR auto ", " fixed " or " off .
342 .br
343 .B Examples :
344 .br
345 .I " iwconfig eth0 frag 512"
346 .br
347 .I " iwconfig eth0 frag off"
348 .TP
349 .BR key / enc [ryption]
350 Used to manipulate encryption or scrambling keys and security mode.
351 .br
352 To set the current encryption key, just enter the key in hex digits as
353 .IR XXXX-XXXX-XXXX-XXXX " or " XXXXXXXX .
354 To set a key other than the current key, prepend or append
355 .I [index]
356 to the key itself (this won't change which is the active key). You can
357 also enter the key as an ASCII string by using the
358 .I s:
359 prefix. Passphrase is currently not supported.
360 .br
361 To change which key is the currently active key, just enter
362 .I [index]
363 (without entering any key value).
364 .br
365 .IR off " and " on
366 disable and reenable encryption.
367 .br
368 The security mode may be
369 .I open
370 or
371 .IR restricted ,
372 and its meaning depends on the card used. With most cards, in
373 .I open
374 mode no authentication is used and the card may also accept
375 non-encrypted sessions, whereas in
376 .I restricted
377 mode only encrypted sessions are accepted and the card will use
378 authentication if available.
379 .br
380 If you need to set multiple keys, or set a key and change the active
381 key, you need to use multiple
382 .B key
383 directives. Arguments can be put in any order, the last one will take
384 precedence.
385 .br
386 .B Examples :
387 .br
388 .I " iwconfig eth0 key 0123-4567-89"
389 .br
390 .I " iwconfig eth0 key [3] 0123-4567-89"
391 .br
392 .I " iwconfig eth0 key s:password [2]"
393 .br
394 .I " iwconfig eth0 key [2]"
395 .br
396 .I " iwconfig eth0 key open"
397 .br
398 .I " iwconfig eth0 key off"
399 .br
400 .I " iwconfig eth0 key restricted [3] 0123456789"
401 .br
402 .I " iwconfig eth0 key 01-23 key 45-67 [4] key [4]"
403 .TP
404 .BR power
405 Used to manipulate power management scheme parameters and mode.
406 .br
407 To set the period between wake ups, enter
408 .IR "period `value'" .
409 To set the timeout before going back to sleep, enter
410 .IR "timeout `value'" .
411 To set the generic level of power saving, enter
412 .IR "saving `value'" .
413 You can also add the
414 .IR min " and " max
415 modifiers. By default, those values are in seconds, append the suffix
416 m or u to specify values in milliseconds or microseconds. Sometimes,
417 those values are without units (number of beacon periods, dwell,
418 percentage or similar).
419 .br
420 .IR off " and " on
421 disable and reenable power management. Finally, you may set the power
422 management mode to
423 .I all
424 (receive all packets),
425 .I unicast
426 (receive unicast packets only, discard multicast and broadcast) and
427 .I multicast
428 (receive multicast and broadcast only, discard unicast packets).
429 .br
430 .B Examples :
431 .br
432 .I " iwconfig eth0 power period 2"
433 .br
434 .I " iwconfig eth0 power 500m unicast"
435 .br
436 .I " iwconfig eth0 power timeout 300u all"
437 .br
438 .I " iwconfig eth0 power saving 3"
439 .br
440 .I " iwconfig eth0 power off"
441 .br
442 .I " iwconfig eth0 power min period 2 power max period 4"
443 .TP
444 .BR modu [lation]
445 Force the card to use a specific set of modulations. Modern cards
446 support various modulations, some which are standard, such as 802.11b
447 or 802.11g, and some proprietary. This command force the card to only
448 use the specific set of modulations listed on the command line. This
449 can be used to fix interoperability issues.
450 .br
451 The list of available modulations depend on the card/driver and can be
452 displayed using
453 .IR "iwlist modulation" .
454 Note that some card/driver may not be able to select each modulation
455 listed independantly, some may come as a group. You may also set this
456 parameter to
457 .IR auto
458 let the card/driver do its best.
459 .br
460 .B Examples :
461 .br
462 .I " iwconfig eth0 modu 11g"
463 .br
464 .I " iwconfig eth0 modu CCK OFDMa"
465 .br
466 .I " iwconfig eth0 modu auto"
467 .TP
468 .BR commit
469 Some cards may not apply changes done through Wireless Extensions
470 immediately (they may wait to aggregate the changes or apply it only
471 when the card is brought up via
472 .IR ifconfig ).
473 This command (when available) forces the card to apply all pending
474 changes.
475 .br
476 This is normally not needed, because the card will eventually apply
477 the changes, but can be useful for debugging.
478 .\"
479 .\" DISPLAY part
480 .\"
481 .SH DISPLAY
482 For each device which supports wireless extensions,
483 .I iwconfig
484 will display the name of the
485 .B MAC protocol
486 used (name of device for proprietary protocols), the
487 .B ESSID
488 (Network Name), the
489 .BR NWID ,
490 the
491 .B frequency
492 (or channel), the
493 .BR sensitivity ,
494 the
495 .B mode
496 of operation, the
497 .B Access Point
498 address, the
499 .BR bit-rate ,
500 the
501 .BR "RTS threshold" ", the " "fragmentation threshold" ,
502 the
503 .B encryption key
504 and the
505 .B power management
506 settings (depending on availability).
507 .PP
508 The parameters displayed have the same meaning and values as the
509 parameters you can set, please refer to the previous part for a
510 detailed explanation of them.
511 .br
512 Some parameters are only displayed in short/abbreviated form (such as
513 encryption). You may use
514 .IR iwlist (8)
515 to get all the details.
516 .br
517 Some parameters have two modes (such as bitrate). If the value is
518 prefixed by
519 .RB ` = ',
520 it means that the parameter is fixed and forced to that value, if it
521 is prefixed by
522 .RB ` : ',
523 the parameter is in automatic mode and the current value is shown (and
524 may change).
525 .TP
526 .BR "Access Point" / Cell
527 An address equal to 00:00:00:00:00:00 means that the card failed to
528 associate with an Access Point (most likely a configuration
529 issue). The
530 .B Access Point
531 parameter will be shown as
532 .B Cell
533 in ad-hoc mode (for obvious reasons), but otherwise works the same.
534 .PP
535 If
536 .I /proc/net/wireless
537 exists,
538 .I iwconfig
539 will also display its content. Note that those values will depend on
540 the driver and the hardware specifics, so you need to refer to your
541 driver documentation for proper interpretation of those values.
542 .TP
543 .B Link quality
544 Overall quality of the link. May be based on the level of contention
545 or interference, the bit or frame error rate, how good the received
546 signal is, some timing synchronisation, or other hardware metric. This
547 is an aggregate value, and depends totally on the driver and hardware.
548 .TP
549 .B Signal level
550 Received signal strength (RSSI - how strong the received signal
551 is). May be arbitrary units or dBm,
552 .I iwconfig
553 uses driver meta information to interpret the raw value given by
554 .I /proc/net/wireless
555 and display the proper unit or maximum value (using 8 bit arithmetic). In
556 .I Ad-Hoc
557 mode, this may be undefined and you should use
558 .IR iwspy .
559 .TP
560 .B Noise level
561 Background noise level (when no packet is transmitted). Similar
562 comments as for
563 .BR "Signal level" .
564 .TP
565 .B Rx invalid nwid
566 Number of packets received with a different NWID or ESSID. Used to
567 detect configuration problems or adjacent network existence (on the
568 same frequency).
569 .TP
570 .B Rx invalid crypt
571 Number of packets that the hardware was unable to decrypt. This can be
572 used to detect invalid encryption settings.
573 .TP
574 .B Rx invalid frag
575 Number of packets for which the hardware was not able to properly
576 re-assemble the link layer fragments (most likely one was missing).
577 .TP
578 .B Tx excessive retries
579 Number of packets that the hardware failed to deliver. Most MAC
580 protocols will retry the packet a number of times before giving up.
581 .TP
582 .B Invalid misc
583 Other packets lost in relation with specific wireless operations.
584 .TP
585 .B Missed beacon
586 Number of periodic beacons from the Cell or the Access Point we have
587 missed. Beacons are sent at regular intervals to maintain the cell
588 coordination, failure to receive them usually indicates that the card
589 is out of range.
590 .\"
591 .\" AUTHOR part
592 .\"
593 .SH AUTHOR
594 Jean Tourrilhes \- jt@hpl.hp.com
595 .\"
596 .\" FILES part
597 .\"
598 .SH FILES
599 .I /proc/net/wireless
600 .\"
601 .\" SEE ALSO part
602 .\"
603 .SH SEE ALSO
604 .BR ifconfig (8),
605 .BR iwspy (8),
606 .BR iwlist (8),
607 .BR iwevent (8),
608 .BR iwpriv (8),
609 .BR wireless (7).