Manual browser: rtw(4)

RTW(4) Kernel Interfaces Manual RTW(4)


rtwRealtek RTL8180L IEEE 802.11b wireless network driver


rtw* at cardbus? function ?
rtw* at pci? dev ? function ?


The rtw driver supports PCI/CardBus 802.11b wireless adapters based on the Realtek RTL8180L.

A variety of radio transceivers can be found in these devices, including the Philips SA2400A, Maxim MAX2820, and GCT GRF5101, though not all of them are currently supported.

These are the modes the rtw driver can operate in:

BSS mode
Also known as infrastructure mode, this is used when associating with an access point, through which all traffic passes. This mode is the default.
IBSS mode
Also known as IEEE ad-hoc mode or peer-to-peer mode. This is the standardized method of operating without an access point. Stations associate with a service set. However, actual connections between stations are peer-to-peer.
Host AP
In this mode the driver acts as an access point (base station) for other cards.
monitor mode
In this mode the driver is able to receive packets without associating with an access point. This disables the internal receive filter and enables the card to capture packets from networks which it wouldn't normally have access to, or to scan for access points.

rtw supports software WEP. Wired Equivalent Privacy (WEP) is the de facto encryption standard for wireless networks. It can be typically configured in one of three modes: no encryption; 40-bit encryption; or 104-bit encryption. Unfortunately, due to serious weaknesses in WEP protocol it is strongly recommended that it not be used as the sole mechanism to secure wireless communication. WEP is not enabled by default.


The rtw driver can be configured at runtime with ifconfig(8) or on boot with ifconfig.if(5) using the following parameters:
bssid bssid
Set the desired BSSID.
Unset the desired BSSID. The interface will automatically select a BSSID in this mode, which is the default.
chan n
Set the channel (radio frequency) to be used by the driver based on the given channel ID n.
Unset the desired channel to be used by the driver. The driver will automatically select a channel in this mode, which is the default.
media media
The rtw driver supports the following media types:

Enable autoselection of the media type and options.
Set 802.11b DS 1Mbps operation.
Set 802.11b DS 2Mbps operation.
Set 802.11b DS 5.5Mbps operation.
Set 802.11b DS 11Mbps operation.
mediaopt opts
The rtw driver supports the following media options:

Select Host AP operation.
Select IBSS operation.
Select monitor mode.
-mediaopt opts
Disable the specified media options on the driver and return it to the default mode of operation (BSS).
ssid id
Set the network ID. The id can either be any text string up to 32 characters in length, or a series of hexadecimal digits up to 64 digits. An empty id string allows the interface to connect to any available access points. By default the rtw driver uses an empty string. Note that network ID is synonymous with Extended Service Set ID (ESSID).
nwkey key
Enable WEP encryption using the specified key. The key can either be a string, a series of hexadecimal digits (preceded by ‘0x’), or a set of keys of the form “n:k1,k2,k3,k4”, where ‘n’ specifies which of the keys will be used for transmitted packets, and the four keys, “k1” through “k4”, are configured as WEP keys. If a set of keys is specified, a comma (‘,’) within the key must be escaped with a backslash. Note that if multiple keys are used, their order must be the same within the network. rtw is capable of using both 40-bit (5 characters or 10 hexadecimal digits) or 104-bit (13 characters or 26 hexadecimal digits) keys.
Disable WEP encryption. This is the default mode of operation.
nwkey persist
Enable WEP encryption with the persistent key stored in the network card.


The following adapters should work:

Card Bus
Belkin F5D6020 V3 CardBus
Buffalo WLI-CB-B11 CardBus
Corega CG-WLCB11V3 CardBus
D-Link DWL-610 CardBus
Level-One WPC-0101 CardBus
Linksys WPC11 v4 CardBus
Netgear MA521 CardBus
Ovislink AirLive WL-1120PCM CardBus
Planet WL-3553 CardBus
TrendNET TEW-266PC CardBus
VCTnet PC-11B1 CardBus


The following ifconfig.if(5) example creates a host-based access point on boot:

inet NONE media autoselect \ 
	mediaopt hostap ssid my_net chan 11

Configure rtw0 for WEP, using hex key “0x1deadbeef1”:

# ifconfig rtw0 nwkey 0x1deadbeef1

Return rtw0 to its default settings:

# ifconfig rtw0 -bssid -chan media autoselect \ 
	ssid "" -nwkey

Join an existing BSS network, “my_net”:

# ifconfig rtw0 netmask 0xffffff00 ssid my_net


The rtw device driver first appeared in NetBSD 3.0 and then in OpenBSD 3.7.


The rtw driver was written by David Young <> and ported to OpenBSD by Jonathan Gray <>, who wrote this man page.


Only the Philips SA2400A and Maxim MAX2820 RF transceivers are known to work. Devices incorporating a GCT RF transceiver are not supported due to a lack of documentation from GCT.

While PCI devices will attach most of them are not able to transmit.

December 29, 2004 NetBSD 7.0