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 [modu M] [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 Set the Network ID. As all adjacent wireless networks share the
47 same medium, this parameter is used to differentiate them (cre‐
48 ate logical colocated networks) and identify nodes belonging to
49 the same cell.
50 This parameter is only used for pre-802.11 hardware, the 802.11
51 protocol uses the ESSID and AP Address for this function.
52 With some cards, you may disable the Network ID checking (NWID
53 promiscuous) with off (and on to reenable it).
54 Examples :
55 iwconfig eth0 nwid AB34
56 iwconfig eth0 nwid off
57 nick[name]
59 Set the nickname, or the station name. Some 802.11 products do
60 define it, but this is not used as far as the protocols (MAC,
61 IP, TCP) are concerned and completely useless as far as configu‐
62 ration goes. Only some wireless diagnostic tools may use it.
63 Example :
64 iwconfig eth0 nickname "My Linux Node"
65 mode Set the operating mode of the device, which depends on the net‐
67 work topology. The mode can be Ad-Hoc (network composed of only
68 one cell and without Access Point), Managed (node connects to a
69 network composed of many Access Points, with roaming), Master
70 (the node is the synchronisation master or acts as an Access
71 Point), Repeater (the node forwards packets between other wire‐
72 less nodes), Secondary (the node acts as a backup mas‐
73 ter/repeater), Monitor (the node is not associated with any cell
74 and passively monitor all packets on the frequency) or Auto.
75 Example :
76 iwconfig eth0 mode Managed
77 iwconfig eth0 mode Ad-Hoc
78 freq/channel
80 Set the operating frequency or channel in the device. A value
81 below 1000 indicates a channel number, a value greater than 1000
82 is a frequency in Hz. You may append the suffix k, M or G to the
83 value (for example, "2.46G" for 2.46 GHz frequency), or add
84 enough '0'.
85 Channels are usually numbered starting at 1, and you may use
86 iwlist(8) to get the total number of channels, list the avail‐
87 able frequencies, and display the current frequency as a chan‐
88 nel. Depending on regulations, some frequencies/channels may not
89 be available.
90 When using Managed mode, most often the Access Point dictates
91 the channel and the driver may refuse the setting of the fre‐
92 quency. In Ad-Hoc mode, the frequency setting may only be used
93 at initial cell creation, and may be ignored when joining an
94 existing cell.
95 You may also use off or auto to let the card pick up the best
96 channel (when supported).
97 Examples :
98 iwconfig eth0 freq 2422000000
99 iwconfig eth0 freq 2.422G
100 iwconfig eth0 channel 3
101 iwconfig eth0 channel auto
102 ap Force the card to register to the Access Point given by the
104 address, if it is possible. This address is the cell identity of
105 the Access Point, as reported by wireless scanning, which may be
106 different from its network MAC address. If the wireless link is
107 point to point, set the address of the other end of the link. If
108 the link is ad-hoc, set the cell identity of the ad-hoc network.
109 When the quality of the connection goes too low, the driver may
110 revert back to automatic mode (the card selects the best Access
111 Point in range).
112 You may also use off to re-enable automatic mode without chang‐
113 ing the current Access Point, or you may use any or auto to
114 force the card to reassociate with the currently best Access
115 Point.
116 Example :
117 iwconfig eth0 ap 00:60:1D:01:23:45
118 iwconfig eth0 ap any
119 iwconfig eth0 ap off
120 rate/bit[rate]
122 For cards supporting multiple bit rates, set the bit-rate in
123 b/s. The bit-rate is the speed at which bits are transmitted
124 over the medium, the user speed of the link is lower due to
125 medium sharing and various overhead.
126 You may append the suffix k, M or G to the value (decimal multi‐
127 plier : 10^3, 10^6 and 10^9 b/s), or add enough '0'. Values
128 below 1000 are card specific, usually an index in the bit-rate
129 list. Use auto to select automatic bit-rate mode (fallback to
130 lower rate on noisy channels), which is the default for most
131 cards, and fixed to revert back to fixed setting. If you specify
132 a bit-rate value and append auto, the driver will use all bit-
133 rates lower and equal than this value.
134 Examples :
135 iwconfig eth0 rate 11M
136 iwconfig eth0 rate auto
137 iwconfig eth0 rate 5.5M auto
138 txpower
140 For cards supporting multiple transmit powers, sets the transmit
141 power in dBm. If W is the power in Watt, the power in dBm is P =
142 30 + 10.log(W). If the value is postfixed by mW, it will be
143 automatically converted to dBm.
144 In addition, on and off enable and disable the radio, and auto
145 and fixed enable and disable power control (if those features
146 are available).
147 Examples :
148 iwconfig eth0 txpower 15
149 iwconfig eth0 txpower 30mW
150 iwconfig eth0 txpower auto
151 iwconfig eth0 txpower off
152 sens Set the sensitivity threshold. This define how sensitive is the
154 card to poor operating conditions (low signal, interference).
155 Positive values are assumed to be the raw value used by the
156 hardware or a percentage, negative values are assumed to be dBm.
157 Depending on the hardware implementation, this parameter may
158 control various functions.
159 On modern cards, this parameter usually control handover/roaming
160 threshold, the lowest signal level for which the hardware
161 remains associated with the current Access Point. When the sig‐
162 nal level goes below this threshold the card starts looking for
163 a new/better Access Point. Some cards may use the number of
164 missed beacons to trigger this. For high density of Access
165 Points, a higher threshold make sure the card is always associ‐
166 ated with the best AP, for low density of APs, a lower threshold
167 minimise the number of failed handoffs.
168 On more ancient card this parameter usually controls the defer
169 threshold, the lowest signal level for which the hardware con‐
170 siders the channel busy. Signal levels above this threshold make
171 the hardware inhibits its own transmission whereas signals
172 weaker than this are ignored and the hardware is free to trans‐
173 mit. This is usually strongly linked to the receive threshold,
174 the lowest signal level for which the hardware attempts packet
175 reception. Proper setting of these thresholds prevent the card
176 to waste time on background noise while still receiving weak
177 transmissions. Modern designs seems to control those thresholds
178 automatically.
179 Example :
180 iwconfig eth0 sens -80
181 iwconfig eth0 sens 2
182 retry Most cards have MAC retransmissions, and some allow to set the
184 behaviour of the retry mechanism.
185 To set the maximum number of retries, enter limit `value'. This
186 is an absolute value (without unit), and the default (when noth‐
187 ing is specified). To set the maximum length of time the MAC
188 should retry, enter lifetime `value'. By defaults, this value
189 in in seconds, append the suffix m or u to specify values in
190 milliseconds or microseconds.
191 You can also add the short, long, min and max modifiers. If the
192 card supports automatic mode, they define the bounds of the
193 limit or lifetime. Some other cards define different values
194 depending on packet size, for example in 802.11 min limit is the
195 short retry limit (non RTS/CTS packets).
196 Examples :
197 iwconfig eth0 retry 16
198 iwconfig eth0 retry lifetime 300m
199 iwconfig eth0 retry short 12
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'. To set the generic level of power saving, enter saving
265 `value'. You can also add the min and max modifiers. By
266 default, those values are in seconds, append the suffix m or u
267 to specify values in milliseconds or microseconds. Sometimes,
268 those values are without units (number of beacon periods, dwell,
269 percentage or similar).
270 off and on disable and reenable power management. Finally, you
271 may set the power management mode to all (receive all packets),
272 unicast (receive unicast packets only, discard multicast and
273 broadcast) and multicast (receive multicast and broadcast only,
274 discard unicast packets).
275 Examples :
276 iwconfig eth0 power period 2
277 iwconfig eth0 power 500m unicast
278 iwconfig eth0 power timeout 300u all
279 iwconfig eth0 power saving 3
280 iwconfig eth0 power off
281 iwconfig eth0 power min period 2 power max period 4
282 modu[lation]
284 Force the card to use a specific set of modulations. Modern
285 cards support various modulations, some which are standard, such
286 as 802.11b or 802.11g, and some proprietary. This command force
287 the card to only use the specific set of modulations listed on
288 the command line. This can be used to fix interoperability
289 issues.
290 The list of available modulations depend on the card/driver and
291 can be displayed using iwlist modulation. Note that some
292 card/driver may not be able to select each modulation listed
293 independantly, some may come as a group. You may also set this
294 parameter to auto let the card/driver do its best.
295 Examples :
296 iwconfig eth0 modu 11g
297 iwconfig eth0 modu CCK OFDMa
298 iwconfig eth0 modu auto
299 commit Some cards may not apply changes done through Wireless Exten‐
301 sions immediately (they may wait to aggregate the changes or
302 apply it only when the card is brought up via ifconfig). This
303 command (when available) forces the card to apply all pending
304 changes.
305 This is normally not needed, because the card will eventually
306 apply the changes, but can be useful for debugging.
307
309 For each device which supports wireless extensions, iwconfig will dis‐
310 play the name of the MAC protocol used (name of device for proprietary
311 protocols), the ESSID (Network Name), the NWID, the frequency (or chan‐
312 nel), the sensitivity, the mode of operation, the Access Point address,
313 the bit-rate, the RTS threshold, the fragmentation threshold, the
314 encryption key and the power management settings (depending on avail‐
315 ability).
316 The parameters displayed have the same meaning and values as the param‐
318 eters you can set, please refer to the previous part for a detailed
319 explanation of them.
320 Some parameters are only displayed in short/abbreviated form (such as
321 encryption). You may use iwlist(8) to get all the details.
322 Some parameters have two modes (such as bitrate). If the value is pre‐
323 fixed by `=', it means that the parameter is fixed and forced to that
324 value, if it is prefixed by `:', the parameter is in automatic mode and
325 the current value is shown (and may change).
326 Access Point/Cell
328 An address equal to 00:00:00:00:00:00 means that the card failed
329 to associate with an Access Point (most likely a configuration
330 issue). The Access Point parameter will be shown as Cell in ad-
331 hoc mode (for obvious reasons), but otherwise works the same.
332 If /proc/net/wireless exists, iwconfig will also display its content.
334 Note that those values will depend on the driver and the hardware
335 specifics, so you need to refer to your driver documentation for proper
336 interpretation of those values.
337 Link quality
339 Overall quality of the link. May be based on the level of con‐
340 tention or interference, the bit or frame error rate, how good
341 the received signal is, some timing synchronisation, or other
342 hardware metric. This is an aggregate value, and depends totally
343 on the driver and hardware.
344 Signal level
346 Received signal strength (RSSI - how strong the received signal
347 is). May be arbitrary units or dBm, iwconfig uses driver meta
348 information to interpret the raw value given by /proc/net/wire‐
349 less and display the proper unit or maximum value (using 8 bit
350 arithmetic). In Ad-Hoc mode, this may be undefined and you
351 should use iwspy.
352 Noise level
354 Background noise level (when no packet is transmitted). Similar
355 comments as for Signal level.
356 Rx invalid nwid
358 Number of packets received with a different NWID or ESSID. Used
359 to detect configuration problems or adjacent network existence
360 (on the same frequency).
361 Rx invalid crypt
363 Number of packets that the hardware was unable to decrypt. This
364 can be used to detect invalid encryption settings.
365 Rx invalid frag
367 Number of packets for which the hardware was not able to prop‐
368 erly re-assemble the link layer fragments (most likely one was
369 missing).
370 Tx excessive retries
372 Number of packets that the hardware failed to deliver. Most MAC
373 protocols will retry the packet a number of times before giving
374 up.
375 Invalid misc
377 Other packets lost in relation with specific wireless opera‐
378 tions.
379 Missed beacon
381 Number of periodic beacons from the Cell or the Access Point we
382 have missed. Beacons are sent at regular intervals to maintain
383 the cell coordination, failure to receive them usually indicates
384 that the card is out of range.
385
387 Jean Tourrilhes - jt@hpl.hp.com
388
390 /proc/net/wireless
391
393 ifconfig(8), iwspy(8), iwlist(8), iwevent(8), iwpriv(8), wireless(7).
394wireless-tools 30 March 2006 IWCONFIG(8)