This translation is older than the original page and might be outdated. See what has changed.

FIXME This page is not fully translated, yet. Please help completing the translation.
(remove this paragraph once the translation is finished)

Wi-Fi /etc/config/wireless

通过UCI配置wireless产生的配置文件位于 /etc/config/wireless.

如果设备有有线以太网端口, 无线wireless默认设置为 OFF 状态. 你可以在 /etc/config/wireless 中打开它,通过将 option disabled '1' 设置为 option disabled '0' (注释或删除掉该行也可以).

A typical wireless config file contains at least a pair of:

  • wifi device (specifying general radio properties like channel, driver type and txpower)
  • wifi interface (defining a wireless network on top of the wifi device).

The wifi-device refer to physical radio devices present on the system. The options present in this section describe properties common across all wireless interfaces on this radio device, such as channel or antenna selection.

A minimal wifi-device declaration may look like the example below. Note that identifiers and options may vary for different chipset types or drivers.

config	wifi-device	'wl0'
	option	type	'broadcom'
	option	channel	'6'
  • wl0 is the internal identifier for the wireless adapter
  • broadcom specifies the chipset/driver type
  • 6 is the wireless channel the device operates on

The possible options for device sections are listed in the table below. Note that not all options are used for all chipset/driver types, refer to the comments for further details.

Name Type Required Default Description
type string yes (autodetected) The type is determined on firstboot during the initial radio device detection - it is usually not required to change it. Used values are broadcom on brcm47xx, or mac80211 for all other platforms
phy string no/yes (autodetected) Specifies the radio phy associated to this section. If present, it is usually autodetected and should not be changed.
macaddr MAC address yes/no (autodetected) Specifies the radio adapter associated to this section, it is not used to change the device mac but to identify the underlying interface.
disabled boolean no 0 Disables the radio adapter if set to 1. Removing this option or setting it to 0 will enable the adapter
channel integer or “auto” yes auto Specifies the wireless channel to use. “auto” defaults to the lowest available channel, or utilizes the ACS algorithm depending on hardware/driver support.
channels list no (regulatory domain specific) Use specific channels, when channel is in “auto” mode. This option allows hostapd to select one of the provided channels when a channel should be automatically selected. Channels can be provided as range using hyphen ('-') or individual channels can be specified by space (' ') separated values.
hwmode string no (driver default) Selects the wireless protocol to use, possible values are 11b, 11g, and 11a. Note that 11ng and 11na are not available options, see ticket 17541.
htmode string no (driver default) Specifies the channel width in 802.11n and 802.11ac mode. See this section for details. Possible values are: HT20, HT40-, HT40+, HT40, or VHT20, VHT40, VHT80, VHT160, NOHT disables 11n
chanbw integer no 20 Specifies a narrow channel width in MHz, possible values are: 5, 10, 20
ht_capab string no (driver default) Specifies the available capabilities of the radio. The values are autodetected. See here for options (check vs. the version of hostapd installed on your router using the “refs” link)
txpower integer no (driver default) Specifies the transmission power in dBm
diversity boolean no 1 Enables or disables the automatic antenna selection by the driver
rxantenna integer no (driver default) Specifies the antenna for receiving, the value may be driver specific, usually it is 1 for the first and 2 for the second antenna. Specifying 0 enables automatic selection by the driver if supported. This option has no effect if diversity is enabled
txantenna integer no (driver default) Specifies the antenna for transmitting, values are identical to rxantenna
country varies no (driver default) Specifies the country code, affects the available channels and transmission powers. For type broadcom a two letter country code is used (EN or DE). The madwifi driver expects a numeric code.
country_ie boolean no 1 if country is set, otherwise 0 Enables IEEE 802.11d country IE (information element) advertisement in beacon and probe response frames. This IE contains the country code and channel/power map. Requires country.
distance integer no (driver default) Distance between the ap and the furthest client in meters.
beacon_int integer no 100 (hostapd default) Set the beacon interval. This is the time interval between beacon frames, measured in units of 1.024 ms. hostapd permits this to be set between 15 and 65535. This option only has an effect on ap and adhoc wifi-ifaces
legacy_rates boolean no 1 in stable, 0 development branch 0 = Disallow legacy 802.11b data rates, 1 = Allow legacy 802.11b data rates. Legacy or badly behaving devices may require legacy 802.11b rates to interoperate. Airtime efficiency may be significantly reduced where these are used. It is recommended to not allow 802.11b rates where possible. The basic_rate and supported_rates options overrides this option.
require_mode string no none Sets the minimum client capability level mode that connecting clients must support to be allowed to connect. Overrides and sets legacy_rates to 0 to disable legacy 802.11b data rates. Supported values: n = 802.11n, ac = 802.11ac
cell_density integer no 0 supported in development branch only Configures data rates based on the coverage cell density. Normal configures basic rates to 6, 12, 24 Mbps if legacy_rates is 0, else to 5.5, 11 Mbps. High configures basic rates to 12, 24 Mbps if legacy_rates is 0, else to the 11 Mbps rate. Very High configures 24 Mbps as the basic rate. Supported rates lower than the minimum basic rate are not offered. The basic_rate and supported_rates options overrides this option. 0 = Disabled, 1 = Normal, 2 = High, 3 = Very High
basic_rate list no (hostapd/driver default) Set the basic data rates. Each basic_rate is measured in kb/s. This option only has an effect on ap and adhoc wifi-ifaces. It is recommended to use the cell_density option instead.
supported_rates list no (hostapd/driver default) Set the supported data rates. Each supported rate is measured in kb/s. This option only has an effect on ap and adhoc wifi-ifaces. This must be a superset of the rates set in basic_rate. The minimum basic rate should also be the minimum supported rate. It is recommended to use the cell_density option instead.
log_level integer no 2 Set the log_level. Supported levels are: 0 = Verbose Debugging, 1 = Debugging, 2 = Informational Messages, 3 = Notification, 4 = Warning

:!: The options below are only used by the proprietary Broadcom driver (type broadcom).

Name Type Required Default Description
frameburst boolean no 0 Enables Broadcom frame bursting if supported
maxassoc integer no (driver default) Limits the maximum allowed number of associated clients
slottime integer no (driver default) Slot time in milliseconds

:!: The options below are only used by the Ubiquity Nanostation family of devices.

Name Type Required Default Description
antenna string no (driver default) Selects the antenna, possible values are vertical for internal vertical polarization, horizontal for internal horizontal polarization or external to use the external antenna connector

A complete wireless configuration contains at least one wifi-iface section per adapter to define a wireless network on top of the hardware. Some drivers support multiple wireless networks per device:

  • broadcom if the core revision is greater or equal 9 (see dmesg | grep corerev)
  • mac80211

A minimal example for a wifi-iface declaration is given below.

config	wifi-iface
	option	device		'wl0'
	option	network		'lan'
	option	mode		'ap'
	option	ssid		'MyWifiAP'
	option	encryption	'psk2'
	option	key		'secret passphrase'
  • wl0 is the identifier for the underlying radio hardware
  • lan specifies the network interface that the Wi-Fi is attached to.
  • ap is the opetion mode, Access Point in this example
  • MyWifiAP is the broadcasted SSID
  • psk2 specifies the wireless encryption method, WPA2 PSK here
  • secret passphrase is the secret WPA passphrase, at least 8 characters long

The common configuration option for wifi-iface sections are listed below.

Name Type Required Default Description
ifname string no (driver default) Specifies a custom name for the Wi-Fi interface, which is otherwise automatically named. Maximum length: 15 characters (See Network Basics for more info)
device string yes (first device id) Specifies the used wireless adapter, must refer to one of the defined wifi-device sections
network string yes lan Specifies the network interface to attach the wireless to.
mode string yes ap Selects the operation mode of the wireless network interface controller. Possible values are ap, sta, adhoc, wds, monitor, mesh
disabled boolean no 0 When set to 1, wireless network is disabled.
ssid string yes OpenWrt The broadcasted SSID of the wireless network and for for managed mode the SSID of the network you’re connecting to
bssid BSSID address no (driver default) Override the BSSID of the network, only applicable in adhoc or sta mode. In wds mode specifies the BSSID of another AP to create WDS with.
mesh_id Mesh ID no none The Mesh ID as defined in IEEE 802.11s. If set, the wireless interface will join this mesh network when brought up. If not, it is necessary to invoke iw <iface> mesh join <mesh_id> to join a mesh after the interface is brought up.
hidden boolean no 0 Disables the broadcasting of beacon frames if set to 1 and, in doing so, hides the ESSID. Where the ESSID is hidden, clients may fail to roam and airtime efficiency may be significantly reduced.
isolate boolean no 0 Isolates wireless clients from each other, only applicable in ap mode. See this post for details.
doth boolean no 0 Enables 802.11h support.
wmm boolean no 1 Enables WMM. Where Wi-Fi Multimedia (WMM) Mode QoS is disabled, clients may be limited to 802.11a/802.11g rates. Required for 802.11n/802.11ac/802.11ax.
encryption string no none Wireless encryption method. Possible values are: none, wep, psk, psk2. For WEP station mode the default is “open system” authentication. Use wep+shared or wep+open to force a specific mode.
key integer or string no (none) In any WPA-PSK mode, this is a string that specifies the pre-shared passphrase from which the pre-shared key will be derived. The clear text key has to be 8-63 characters long. If a 64-character hexadecimal string is supplied, it will be used directly as the pre-shared key instead. In WEP mode, this can be an integer specifying which key index to use (key1, key2, key3, or key4.) Alternatively, it can be a string specifying a passphrase or key directly, as in key1. In any WPA-Enterprise AP mode, this option has a different interpretation.
key1 string no (none) WEP passphrase or key #1 (selected by the index in key). This string is treated as a passphrase from which the WEP key will be derived. If a 10- or 26-character hexadecimal string is supplied, it will be used directly as the WEP key instead.
key2 string no (none) WEP passphrase or key #2 (selected by the index in key), as in key1.
key3 string no (none) WEP passphrase or key #3 (selected by the index in key), as in key1.
key4 string no (none) WEP passphrase or key #4 (selected by the index in key), as in key1.
macfilter string no disable Specifies the mac filter policy, disable to disable the filter, allow to treat it as whitelist or deny to treat it as blacklist.
maclist list of MAC addresses no (none) List of MAC addresses (divided by spaces) to put into the mac filter.
iapp_interface string no (none) Specifies a network interface to be used for 802.11f (IAPP) - only enabled when defined.
rsn_preauth boolean no 0 Allow preauthentication for WPA2-EAP networks (and advertise it in WLAN beacons). Only works if the specified network interface is a bridge.
ieee80211w integer no 0 Enables MFP (802.11w) support (0 = disabled, 1 = optional, 2 = required). Requires the 'full' version of wpad/hostapd and support from the Wi-Fi driver
ieee80211w_max_timeout integer no (hostapd default) Specifies the 802.11w Association SA Query maximum timeout.
ieee80211w_retry_timeout integer no (hostapd default) Specifies the 802.11w Association SA Query retry timeout.
maxassoc integer no (hostapd/driver default) Specifies the maximum number of clients to connect.
macaddr mac address no (hostapd/driver default) Overrides the MAC address used for the Wi-Fi interface. Warning: if the MAC address specified is a multicast address, this override will fail silently. To avoid this problem, ensure that the mac address specified is a valid unicast mac address.
dtim_period integer no 2 (hostapd default) Set the DTIM (delivery traffic information message) period. There will be one DTIM per this many beacon frames. This may be set between 1 and 255. This option only has an effect on ap wifi-ifaces.
short_preamble boolean no 1 Set optional use of short preamble
max_listen_int integer no 65535 (hostapd default) Set the maximum allowed STA (client) listen interval. Association will be refused if a STA attempts to associate with a listen interval greater than this value. This option only has an effect on ap wifi-ifaces.
mcast_rate integer no (driver default) Sets the fixed multicast rate, measured in kb/s. Only supported in adhoc and mesh modes
wds boolean no 0 This sets 4-address mode
owe_transition_ssid string no none Opportunistic Wireless Encryption (OWE) Transition SSID (only for OPEN and OWE networks)
owe_transition_bssid BSSID address no none Opportunistic Wireless Encryption (OWE) Transition BSSID (only for OPEN and OWE networks)

Besides the WPA mode, the encryption option also specifies the group and peer ciphers to use. To override the cipher, the value of encryption must be given in the form mode+cipher. See the listing below for possible combinations. If the hwmode of the interface is set to ng or na, then the CCMP cipher is always added to the list.

To use the WPA3 modes as access point, it is required to install the hostapd-openssl package.

To use the WPA3 modes as station (client), it is required to install the wpa-supplicant-openssl package.

To support both access point and station modes with WPA3, it is possible to install the wpad-openssl package.

Value WPA Version Ciphers Supported since
sae WPA3 Personal (SAE) CCMP 19.07
sae-mixed WPA2/WPA3 Personal (PSK/SAE) mixed mode CCMP 19.07
psk2+tkip+ccmp WPA2 Personal (PSK) TKIP, CCMP
psk2+tkip+aes WPA2 Personal (PSK) TKIP, CCMP
psk2+tkip WPA2 Personal (PSK) TKIP
psk2+ccmp WPA2 Personal (PSK) CCMP
psk2+aes WPA2 Personal (PSK) CCMP
psk2 WPA2 Personal (PSK) CCMP
psk+tkip+ccmp WPA Personal (PSK) TKIP, CCMP
psk+tkip+aes WPA Personal (PSK) TKIP, CCMP
psk+tkip WPA Personal (PSK) TKIP
psk+ccmp WPA Personal (PSK) CCMP
psk+aes WPA Personal (PSK) CCMP
psk WPA Personal (PSK) CCMP
psk-mixed+tkip+ccmp WPA/WPA2 Personal (PSK) mixed mode TKIP, CCMP
psk-mixed+tkip+aes WPA/WPA2 Personal (PSK) mixed mode TKIP, CCMP
psk-mixed+tkip WPA/WPA2 Personal (PSK) mixed mode TKIP
psk-mixed+ccmp WPA/WPA2 Personal (PSK) mixed mode CCMP
psk-mixed+aes WPA/WPA2 Personal (PSK) mixed mode CCMP
psk-mixed WPA/WPA2 Personal (PSK) mixed mode CCMP
wpa3 WPA3 Enterprise CCMP 19.07
wpa3-mixed WPA3/WPA2 Enterprise CCMP 19.07
wpa2+tkip+ccmp WPA2 Enterprise TKIP, CCMP
wpa2+tkip+aes WPA2 Enterprise TKIP, CCMP
wpa2+ccmp WPA2 Enterprise CCMP
wpa2+aes' WPA2 Enterprise CCMP
wpa2 WPA2 Enterprise CCMP
wpa2+tkip WPA2 Enterprise TKIP
wpa+tkip+ccmp WPA Enterprise TKIP, CCMP
wpa+tkip+aes WPA Enterprise TKIP, AES
wpa+ccmp WPA Enterprise CCMP
wpa+aes WPA Enterprise CCMP
wpa+tkip WPA Enterprise TKIP
wpa WPA Enterprise CCMP
wpa-mixed+tkip+ccmp WPA/WPA2 Enterprise mixed mode TKIP, CCMP
wpa-mixed+tkip+aes WPA/WPA2 Enterprise mixed mode TKIP, CCMP
wpa-mixed+tkip WPA/WPA2 Enterprise mixed mode TKIP
wpa-mixed+ccmp WPA/WPA2 Enterprise mixed mode CCMP
wpa-mixed+aes WPA/WPA2 Enterprise mixed mode CCMP
wpa-mixed WPA/WPA2 Enterprise mixed mode CCMP
owe Opportunistic Wireless Encryption (OWE) CCMP 19.07

Listing of Access Point related options for WPA Enterprise.

Name Default Description
server (none) RADIUS server to handle client authentication
port 1812 RADIUS port
key (none) Shared RADIUS secret
wpa_group_rekey 600 WPA Group Cipher rekeying interval in seconds
auth_server (none) RADIUS authentication server to handle client authentication
auth_port 1812 RADIUS authentication port
auth_secret (none) Shared authentication RADIUS secret
auth_cache 0 Disable or enable PMKSA and Opportunistic Key Caching
acct_server (none) RADIUS accounting server to handle client authentication
acct_port 1813 RADIUS accounting port
acct_secret (none) Shared accounting RADIUS secret
nasid (none) NAS ID to use for RADIUS authentication requests
ownip (none) NAS IP Address to use for RADIUS authentication requests
dae_client (none) Dynamic Authorization Extension client. This client can send “Disconnect-Request” or “CoA-Request” packets to forcibly disconnect a client or change connection parameters.
dae_port 3799 Port the Dynamic Authorization Extension server listens on.
dae_secret (none) Shared DAE secret.
dynamic_vlan 0 Dynamic VLAN assignment
vlan_naming 1 VLAN Naming
vlan_tagged_interface (none) VLAN Tagged Interface
vlan_bridge (none) VLAN Bridge Naming Scheme - added in

Listing of Client related options for WPA Enterprise.

Name Default Description
eap_type (none) Defines the EAP protocol to use, possible values are tls for EAP-TLS and peap or ttls for EAP-PEAP
auth MSCHAPV2 “auth=PAP”/PAP/MSCHAPV2 - Defines the phase 2 (inner) authentication method to use, only applicable if eap_type is peap or ttls
identity (none) EAP identity to send during authentication
password (none) Password to send during EAP authentication
ca_cert (none) Specifies the path the CA certificate used for authentication
client_cert (none) Specifies the client certificate used for the authentication
priv_key (none) Specifies the path to the private key file used for authentication, only applicable if eap_type is set to tls
priv_key_pwd (none) Password to unlock the private key file, only works in conjunction with priv_key

:!: When using WPA Enterprise type PEAP with Active Directory Servers, the “auth” option must be set to “auth=MSCHAPV2” or “auth=PAP”.

option auth 'auth=MSCHAPV2'


option auth 'auth=PAP'
Name Default Description
wpa_disable_eapol_key_retries 0 Workaround for key reinstallation attacks (requires LEDE 17.01.4 or higher)

Complete description copied from upstream hostapd.conf example:

# Workaround for key reinstallation attacks
# This parameter can be used to disable retransmission of EAPOL-Key frames that
# are used to install keys (EAPOL-Key message 3/4 and group message 1/2). This
# is similar to setting wpa_group_update_count=1 and
# wpa_pairwise_update_count=1, but with no impact to message 1/4 and with
# extended timeout on the response to avoid causing issues with stations that
# may use aggressive power saving have very long time in replying to the
# EAPOL-Key messages.
# This option can be used to work around key reinstallation attacks on the
# station (supplicant) side in cases those station devices cannot be updated
# for some reason. By removing the retransmissions the attacker cannot cause
# key reinstallation with a delayed frame transmission. This is related to the
# station side vulnerabilities CVE-2017-13077, CVE-2017-13078, CVE-2017-13079,
# CVE-2017-13080, and CVE-2017-13081.
# This workaround might cause interoperability issues and reduced robustness of
# key negotiation especially in environments with heavy traffic load due to the
# number of attempts to perform the key exchange is reduced significantly. As
# such, this workaround is disabled by default (unless overridden in build
# configuration). To enable this, set the parameter to 1.

Note that this workaround can't prevent attacks against Tunneled Direct-Link Setup (TDLS). You may also want to add the option tdls_prohibit=1 in order to make such an attack more complicated:

Name Default Description
tdls_prohibit 0 Prohibit the use of TDLS on the network (complicates key reinstallation attacks against TDLS) (requires hostapd/wpad 2016-12-19-ad02e79d-7 or higher)

Listing of Wi-Fi Protected Setup related options.

:!: Support for WPS is provided by packages wpad and hostapd-utils. Default package wpad-mini is not enough.

:!: WPS is possible only when encryption PSK/PSK2 is selected.

Name Type Required Default Description
wps_config list no (none) List of configuration methods. Currentlly supported methods are: push_button.
wps_device_name string no LEDE AP User-friendly description of device; up to 32 octets encoded in UTF-8.
wps_device_type string no 6-0050F204-1 Primary device type. Examples: 1-0050F204-1 (Computer / PC), 1-0050F204-2 (Computer / Server), 5-0050F204-1 (Storage / NAS), 6-0050F204-1 (Network Infrastructure / AP)
wps_label boolean no 0 Enable label configuration method.
wps_manufacturer string no The manufacturer of the device (up to 64 ASCII characters).
wps_pushbutton boolean no 0 Enable push-button configuration method.
wps_pin string no none The PIN to use with WPS-PIN (only in external registrar mode?)

Minimal steps needed to get WPS running:

  • Add option wps_pushbutton '1 ' to a config wifi-iface section that is configured for WPA2-PSK in /etc/config/wireless
  • opkg update
  • opkg remove wpad-mini
  • opkg install wpad hostapd-utils
  • reboot

After rebooting, instead of pushing the WPS button, you can manually initiate the WPS process (which is safer than using the button if it doubles as a reset button):

hostapd_cli wps_pbc

When using WPS-PIN:

  • Add option wps_label '1 ' to a config wifi-iface section that is configured for WPA2-PSK in /etc/config/wireless
  • opkg update
  • opkg remove wpad-mini
  • opkg install wpad hostapd-utils
  • reboot

After rebooting, the WPS PIN needs to be given to hostapd each time a station tries to connect. The PIN may NOT be used multiple times, as an active attacker can recover half of it during each try. The “any” keyword can be replaced by the specific stations EUUID, as printed in hostapd log.

hostapd_cli wps_pin any $PIN


# /etc/config/wireless
config wifi-iface
	option device 'radio0'
	option mode 'ap'
	option ssid 'My-WiFi-Home'
	option network 'lan'
	option encryption 'psk2'
	option key 'WiFipassword'
	option ieee80211w '0'
	option wps_pushbutton '1'
Name Type Required Default Description
ieee80211v boolean no 0 Enables BSS transition (802.11v) support.
time_advertisement integer no 0 Time advertisement. 0 is disabled (see hostapd's time_advertisement setting).
wnm_sleep_mode boolean no 0 WNM-Sleep Mode (extended sleep mode for stations).
bss_transition boolean no 0 BSS Transition Management.
Name Type Required Default Description
ieee80211r boolean no 0 Enables fast BSS transition (802.11r) support.
nasid string yes (none) PMK-R0 Key Holder identifier (dot11FTR0KeyHolderID). A 1 to 48 octet identifier.
mobility_domain string no 4f57 Mobility Domain identifier (dot11FTMobilityDomainID, MDID). MDID is used to indicate a group of APs (within an ESS, i.e., sharing the same SSID) between which a STA can use Fast BSS Transition. 2-octet identifier as a hex string.
r0_key_lifetime integer no 10000 Default lifetime of the PMK-RO in minutes [1-65535].
r1_key_holder string no 00004f577274 PMK-R1 Key Holder identifier (dot11FTR1KeyHolderID). A 6-octet identifier as a hex string.
reassociation_deadline integer no 1000 Reassociation deadline in time units (TUs / 1.024 ms, 1000-65535)
r0kh string no (none) List of R0KHs in the same Mobility Domain. Valid format: <MAC address>,<NAS Identifier>,<128-bit key as hex string> This list is used to map R0KH-ID (NAS Identifier) to a destination MAC address when requesting PMK-R1 key from the R0KH that the STA used during the Initial Mobility Domain Association.
r1kh string no (none) List of R1KHs in the same Mobility Domain. Valid format: <MAC address>,<R1KH-ID>,<128-bit key as hex string> This list is used to map R1KH-ID to a destination MAC address when sending PMK-R1 key from the R0KH. This is also the list of authorized R1KHs in the MD that can request PMK-R1 keys.
pmk_r1_push boolean no 0 Whether PMK-R1 push is enabled at R0KH.
ft_over_ds boolean no 1 Whether to enable FT-over-DS.
ft_psk_generate_local boolean no 0 Whether to generate FT response locally for PSK networks. This avoids use of PMK-R1 push/pull from other APs with FT-PSK networks as the required information (PSK and other session data) is already locally available.
Name Type Required Default Description
disassoc_low_ack boolean no 1 Disassociate stations based on excessive transmission failures or other indications of connection loss. This depends on the driver capabilities and may not be available with all drivers.
max_inactivity integer no 300 Station inactivity limit in seconds: If a station does not send anything in ap_max_inactivity seconds, an empty data frame is sent to it in order to verify whether it is still in range. If this frame is not ACKed, the station will be disassociated and then deauthenticated.
skip_inactivity_poll boolean no 0 The inactivity polling can be disabled to disconnect stations based on inactivity timeout so that idle stations are more likely to be disconnected even if they are still in range of the AP.
max_listen_interval integer no 65535 Maximum allowed Listen Interval (how many Beacon periods STAs are allowed to remain asleep).

Wireless interfaces are brought up and down with the wifi command. To (re)start the wireless after a configuration change, use wifi, to disable the wireless, run wifi down. In case your platform carries multiple wireless devices it is possible to start or run down each of them individually by making the wifi command be followed by the device name as a second parameter. Note: The wifi command has an optional first parameter that defaults to up , i.e. start the device. To make the second parameter indeed a second parameter it is mandatory to give a first parameter which can be anything except down. E.g. to start the interface wlan2 issue: wifi up wlan2; to stop that interface: wifi down wlan2. If the platform has also e.g. wlan0 and wlan1 these will not be touched by stopping or starting wlan2 selectively.

To rebuild the configuration file, e.g. after installing a new wireless driver, remove the existing wireless configuration (if any) and use the wifi config command:

rm -f /etc/config/wireless
wifi config

The Wi-Fi channel width is the range of frequencies i.e. how broad the signal is for transferring data. Generally speaking, the bigger the channel width, the more data can be transmitted over the signal. But as with everything there are drawbacks. With larger channel widths, interference with others Wi-Fi networks or Bluetooth becomes a much larger issue, and making solid connections becomes much harder as well. Think of it like a highway. The wider the road, the more traffic (data) can pass through. On the other hand, the more cars (routers) you have on the road, the more congested the traffic becomes.

Wi-Fi standard allows 10, 20, 22, 40, 80 and 160 MHz but 10MHz is not used anymore, the 80 and 160 can be used only with 5 GHz frequency, and certain devices not being able to connect to APs with channel widths more than 40Mhz.

By default, the 2.4 GHz frequency uses a 20 MHz channel width. A 20MHz channel width is wide enough to span one channel. A 40 MHz channel width bonds two neighbouring 20 MHz channels together, forming a 40 MHz channel width; therefore, it allows for greater speed and faster transfer rates. One “control” channel functions as the main channel, and the other “extension” as the auxiliary channel. The main channel sends Beacon packets and data packets, and the auxiliary channel sends other packets. The extension channel can either be “above” or “below” the control channel, as long as it doesn't go outside the band. For example, if your control channel is 1, your extension channel has to “above”, because anything below channel 1 would be below the lowest frequency allowed in the 2.4GHz ISM band. The extension channel has to be contiguous with the edge of the control channel, without overlapping.

HT40+ means that centre frequency of the main 20 MHz channel is higher than that of the auxiliary channel, and HT40- otherwise. For example, if the centre frequency 149 and the centre frequency 153 reside on two 20 MHz channels, 149plus indicates that the two 20 MHz channels are bundled to form a 40 MHz channel.

When the HT40 mode is used in the 2.4 GHz frequency band, there is only one non-overlapping channel. Therefore, you are not advised to use the HT40 mode in the 2.4 GHz frequency band.

  • HT20 High Throughput 20MHz, 802.11n
  • HT40 High Throughput 40MHz, 802.11n
  • HT40- High Throughput 40MHz, 802.11n, control channel is bellow extension channel.
  • HT40+ High Throughput 40MHz, 802.11n, control channel is above extension channel.
  • VHT20 Very High Throughput 20MHz, Supported by 802.11ac
  • VHT40 Very High Throughput 40MHz, Supported by 802.11ac
  • VHT80 Very High Throughput 80MHz, Supported by 802.11ac
  • VHT160 Very High Throughput 160MHz, Supported by 802.11ac
  • NOHT disables 11n

The default max channel width VT20 i.e. 20MHz supports a max speed of 150Mbps. Increasing this to 40MHz will increase the maximum theoretical speed to 300Mbps. The catch is that in areas with a lot of Wi-Fi traffic (and Bluetooth etc. which share the same radio frequencies), 40MHz may decrease your overall speed. Devices should detect interference when using 40MHz, and drop back to 20MHz. Edit htmode options in the file /etc/config/wireless and restart the Wi-Fi AP to test various channel widths. Note that option htmode should be set to either HT40+ (for channels 1-7) or HT40- (for channels 5-11) or simply HT40.

In many countries, operating Wi-Fi devices on some or all channels in the 5GHz band requires radar detection and DFS (explanation). If you define a channel in your wireless config that requires DFS according to your country regulations, the 5GHz radio device won’t start up unless the firmware image is able to provide DFS support (i.e. it is both included and enabled). More technical details of the Linux implementation can be found here. DFS works as follows in Linux: The driver detects radar pulses and reports this to nl80211 where the information is processed. If a series of pulses matches one of the defined radar patterns, this will be reported to the user space application (e.g. hostapd) which in turn reacts by switching to another channel.

The following configuration selects channel 104 which needs DFS support as implicitly stated with country code DE:

config	wifi-device		'radio0'
	option	type		'mac80211'
	option	channel		'104'
	option	hwmode		'11a'
	option	path		'pci0000:00/0000:00:00.0'
	option	htmode		'HT20'
	option	country		'DE'
config	wifi-iface
	option	device		'radio0'
	option	network		'lan'
	option	mode		'ap'
	option	ssid		'OpenWrt'
	option	encryption	'none'

You can check the country (regulatory domain) your Wi-Fi card thinks it must conform to with

iw reg get

If in doubt, double check your hostapd-phy.conf to make sure it contains the following values, and that your country code is set:


If radar detection is working, DFS channels will show up like this (here for Belgium, iw phy1 info output trimmed):

* 5220 MHz [44] (17.0 dBm)
* 5240 MHz [48] (17.0 dBm)
* 5260 MHz [52] (20.0 dBm) (radar detection)
DFS state: usable (for 2155257 sec)
DFS CAC time: 60000 ms
* 5280 MHz [56] (20.0 dBm) (radar detection)
DFS state: usable (for 2155257 sec)
DFS CAC time: 60000 ms

:!: When DFS is on, there will be a delay before the interface is enabled (e.g. after reboot). During this time period (often 60 seconds, and determined by local reglations) luci will report the interface is disabled. This time period is used to detect the presence of other signals on the channel (Channel Availability Check Time). This process can be monitored with:

logread -f

If you select a channel that requires DFS in your country and enable HT40, this may result in the DFS start_dfs_cac() failed error (visible with logread):

Configuration file: /var/run/hostapd-phy1.conf
wlan1: interface state UNINITIALIZED->COUNTRY_UPDATE
wlan1: interface state COUNTRY_UPDATE->HT_SCAN
wlan1: interface state HT_SCAN->DFS
wlan1: DFS-CAC-START freq=5680 chan=136 sec_chan=-1, width=0, seg0=0, seg1=0, cac_time=60s
DFS start_dfs_cac() failed, -1
Interface initialization failed
wlan1: interface state DFS->DISABLED
hostapd_free_hapd_data: Interface wlan1 wasn't started

Changing your configuration to HT20 should resolve this.

This website uses cookies. By using the website, you agree with storing cookies on your computer. Also you acknowledge that you have read and understand our Privacy Policy. If you do not agree leave the website.More information about cookies
  • Last modified: 2021/01/28 00:59
  • by shorile