iw is a new nl80211 based CLI configuration utility for wireless devices. It supports all new drivers that have been added to the kernel recently. The old tool iwconfig, which uses Wireless Extensions interface, is deprecated and it's strongly recommended to switch to iw and nl80211.
Like the rest of the Linux kernel, iw is still under development. Features are added 'as we go'. The only documentation for iw is this page and output from 'iw help'. Please help expand this page.
There is a page listing use cases with iwconfig and iw: replacing iwconfig.
Release tarballs of iw are available from http://kernel.org/pub/software/network/iw/.
Alternatively, you can download iw from git: http://git.kernel.org/?p=linux/kernel/git/jberg/iw.git.
on your command line and it will print out the commands it supports.
Use the following to get device capabilities for all devices, such as band information (2.4 GHz, and 5 GHz), and 802.11n information:
iw dev wlan0 scan
When debugging, it can be useful to see the auth/assoc/deauth/disassoc frames, use
iw event -f
and sometimes timing information is also useful:
iw event -t
To determine if you are connected to an AP or not and if you are the last TX rate used you can use the command below.
Example output when associated to a legacy (non-802.11n) AP:
iw dev wlan0 link Connected to 04:21:b0:e8:c8:8b (on wlan0) SSID: attwifi freq: 2437 RX: 2272 bytes (18 packets) TX: 232 bytes (3 packets) signal: -57 dBm tx bitrate: 36.0 MBit/s
Example output when associated to an 802.11n AP:
iw dev wlan0 link Connected to 68:7f:74:3b:b0:01 (on wlan0) SSID: tesla-5g-bcm freq: 5745 RX: 30206 bytes (201 packets) TX: 4084 bytes (23 packets) signal: -31 dBm tx bitrate: 300.0 MBit/s MCS 15 40Mhz short GI
Example output when not connected to an AP:
iw dev wlan0 link Not connected.
This would happen if you are not connected to an AP. To connect to an AP you can use iw connect if the connection requires:
You can use iw to connect to an AP directly if and only if the AP has:
If you do choose to deal with disconnects yourself you can use iw connect as follows.
To connect to an AP that has encryption disabled, where its SSID is foo:
iw wlan0 connect foo
Suppose you have two APs with the SSID foo, and you know the one you want to connect to is on the frequency 2432, you can specify the frequency to use:
iw wlan0 connect foo 2432
To connect to an AP that uses WEP, you can use:
iw wlan0 connect foo keys 0:abcde d:1:0011223344
To get station statistic information such as the amount of tx/rx bytes, the last TX bitrate (including MCS rate) you can do:
$ iw dev wlan1 station dump Station 12:34:56:78:9a:bc (on wlan0) inactive time: 304 ms rx bytes: 18816 rx packets: 75 tx bytes: 5386 tx packets: 21 signal: -29 dBm tx bitrate: 54.0 MBit/s
If you want to get specific statistics against a peer you station is communicating with you can use the following:
sudo iw dev wlan1 station get <peer-MAC-address>
In the case of a STA the above <peer-MAC-address> would be the MAC address of your AP.
iw supports modifying TX bitrates, both legacy and HT MCS rates. It does this by masking in the allowed bitrates, and also lets you clear the mask.
You can set preference for transmitting using only certain legacy bitrates. For example:
iw wlan0 set bitrates legacy-2.4 12 18 24
Here's how to enable what some folks call “Purge G” which disables 802.11b associations:
iw wlan0 set bitrates legacy-2.4 6 12 24
Setting preference for transmitting using MCS rates is supported by letting you specify the band and MCS rate. Note that whether or not the device actually listens to your petition will vary depending on the device driver and cooperation from the firmware. For example:
iw dev wlan0 set bitrates mcs-5 4
iw dev wlan0 set bitrates mcs-2.4 10
To clear all tx bitrates and set things back to normal:
iw dev wlan0 set bitrates mcs-2.4 iw dev wlan0 set bitrates mcs-5
You can set the txpower by using either the device interface name of the respective phy.
iw dev <devname> set txpower <auto|fixed|limit> [<tx power in mBm>] iw phy <phyname> set txpower <auto|fixed|limit> [<tx power in mBm>]
(Note that the value this commands takes is in millibel-milliwatts (mBm) instead of the commonly used decibel-milliwatts (dBm). <power in mBm> = 100 * <power in dBm>)
To enable power save by default you can use:
sudo iw dev wlan0 set power_save on
For mac80211 drivers this means Dynamic Power Save gets enabled.
To query the current power save settings you can use:
iw dev wlan0 get power_save
There are several modes supported. The modes supported are:
For example to add a monitor interface:
iw phy phy0 interface add moni0 type monitor
where you can replace
by anything else and
by the interface name, and need to replace
by the PHY name for your hardware (usually phy0 will be correct unless you hotplugged or reloaded any modules.) If your udev is configured incorrectly, the newly created virtual interface may be renamed by it right away, use
to list all interfaces. To create a new managed mode interface you would use:
iw phy phy0 interface add wlan10 type managed
Note that the interface is automatically put into AP mode when using hostapd.
You can customize the type of monitor interface you create. This can be very useful for debugging purposes on end user systems. For example, suppose you want to help a user. You can take advantage of the fact that a monitor interface in mac80211 uses radiotap to pass up to userspace additional data. Say we want to help a user fish out data without affecting the device's performance by setting it to a full monitor interface. A monitor interface with no additional monitor flags can be created as follows:
iw dev wlan0 interface add fish0 type monitor flags none
You can then request the user to use tcpdump on a session:
tcpdump -i fish0 -s 65000 -p -U -w /tmp/fishing.dump
The nice thing about these type of alternative monitor interfaces is you can further extend radiotap even with vendor extensions to add more data to radiotap to help debug device specific features.
Keep in mind this requires drivers to honor mac80211's flag requests strictly, so drivers like ath5k and ath9k which still enable flags based on operation mode need to be fixed to take advantage of this.
The following are flags you can specify:
iw dev moni0 del
There is a dedicated section for virtual vif support, see the iw vif page.
The command line is:
iw reg set alpha2
You can also use the latest wpa_supplicant (as of 0.6.7) now to change your regulatory domain, to do so just add a “country=US” entry into your configuration for example.
You may add a mesh interface to drivers that support Mesh Point operation. Mesh Point interfaces have a mesh_id parameter which may be up to 32 bytes long. For example, to add an interface “mesh0” to device phy0 with mesh_id “mymesh”,
iw phy phy0 interface add mesh0 type mp mesh_id mymesh
Mesh Point interfaces, by default, are configured on Channel 1. Mesh Point operation begins when the interface is brought up. In the default configuration, Mesh Point interfaces will automatically detect and attempt to create Peer Links with other Mesh Points (peers) having the same mesh ID. Use the station list and station statistics to see the peer list and Peer Link status.
After sending traffic (ex: pinging another mesh node), you may wish to see a list of Mesh Paths:
iw dev mesh0 mpath dump
Please see the open80211s.org HOWTO for further details on Mesh Point related commands and their output, as well as more examples. iw also provides commands for advanced Mesh Point configuration. These are documented in the Advanced Tinkering section of the open80211s HOWTO.
WDS mode is a non-standard extension to the IEEE 802.11 standard to allow transparent Ethernet bridging on the station and to implement seamingless hand-over for wireless clients roaming between different access points. Due to its non-standard nature, WDS is often implemented differently in wireless drivers and vendor firmwares making them incompatible with each other. In order to use WDS, one should use the same hardware and software on all deployed wireless devices to maintain compatibility.
To create a WDS peer you will first need to create an interface of WDS type, and then set the peer:
iw phy phy0 interface add wds0 type wds iw dev wds0 set peer <MAC address>
In order for this to work the driver must implement the cfg80211 callback set_wds_peer(). mac80211 implements this callback, so the respective mac80211 driver would just need to support WDS type interfaces. What WDS will do is replace the first address on the 802.11 header with the peer address when TXing frames. Instead of using WDS though you may want to consider using 4-address mode described below if you have control over the software running on the AP and respective clients/peers connected.
In some situations it might be useful to run a network with an Access Point and multiple clients, but with each client bridged to a network behind it. For this to work, both the client and the AP need to transmit 4-address frames, containing both source and destination MAC addresses. 4-address mode is how OpenWrt supports WDS mode for mac80211 drivers, that is if you enable wds option on your OpenWrt OpenWrt wireless configuration you will end up using 4-address mode. 4-address mode is not compatible with other WDS implementations, ie, you'll need all endpoints using this mode in order for WDS to work appropriately.
Linux wireless has support for 4-address mode for AP and STAs but each driver needs to define this capability explicitly. All mac80211 drivers support 4-address mode if AP or STA modes of operation are supported respectively.
On the AP side you can enable 4-address frames for individual clients by isolating them in separate AP VLANs which are configured in 4-address mode. Such an AP VLAN will be limited to one client only, and this client will be used as the destination for all traffic on its interface, regardless of the destination MAC address in the packet headers. The advantage of this mode compared to regular WDS mode is that it's easier to configure and does not require a static list of peer MAC addresses on any side. 4-address mode is incompatible with WDS.
To enable 4-address mode when creating an interface you should add 4addr on, for example:
iw phy phy0 interface add sta0 type managed 4addr on
In this mode, the new interface can be in a bridge – if it is then you need to use the
flag to wpa_supplicant to make it listen for EAPOL on the bridge instead of the interface itself.
In hostapd you can enable this with the flag on hostapd.conf:
Please note 4-address mode is currently broken on 3.9 because of commit 576eb62598f10c8c7fd75703fe89010cdcfff596 , this topic is currently being addressed on the mailing lists for a resolution.
In most cases, host that receives IPv4 and IPv6 multicast/broadcast packets does not do anything with these packets. Therefore the reception of these unwanted packets causes unnecessary processing and power consumption.
Packet coalesce feature helps to reduce number of receive interrupts to host by buffering these packets in firmware/hardware for some predefined time. Receive interrupt will be generated when one of the following events occur.
Coalesce support: * Maximum 8 coalesce rules supported * Each rule contains upto 4 patterns of 1-4 bytes, maximum packet offset 50 bytes * Maximum supported coalescing delay 100 msecs
You need to configure following parameters for creating a coalesce rule.
To enable coalesce feature using rules listed in coalesce.conf file, you can use:
iw phy phy0 enable coalesce.conf
Where coalesce.conf contains:
delay=25 condition=0 patterns=8+34:xx:ad:22,10+23:45:67,59:33:xx:25,ff:ff:ff:ff delay=40 condition=1 patterns=12+00:xx:12,23:45:67,46:61:xx:50
To display current coalesce configuration, you can use:
$ iw phy phy0 coalesce show Coalesce is enabled: Rule - max coalescing delay: 25msec condition:match * packet offset: 8 pattern: 34:--:ad:22 * packet offset: 10 pattern: 23:45:67 * packet offset: 0 pattern: 59:33:--:25 * packet offset: 0 pattern: ff:ff:ff:ff Rule - max coalescing delay: 40msec condition:not match * packet offset: 12 pattern: 00:--:12 * packet offset: 0 pattern: 23:45:67 * packet offset: 0 pattern: 46:61:--:50
To disable coalesce feature, you can use:
iw phy phy0 coalesce disable
'iw display' output when coalesce is not configured:
$ iw phy phy0 coalesce show Coalesce is disabled.