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RTWN(4) Device Drivers Manual RTWN(4)

Realtek RTL8188CE PCIe IEEE 802.11b/g/n wireless network device

rtwn* at pci? port ?

The rtwn driver supports PCIe wireless network devices based on the Realtek RTL8188CE chipset.

The RTL8188CE is a highly integrated 802.11n adapter that combines a MAC, a 1T1R capable baseband and an RF in a single chip. It operates in the 2GHz spectrum only.

These are the modes the rtwn 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.
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.

The rtwn driver can be configured to use Wired Equivalent Privacy (WEP) or Wi-Fi Protected Access (WPA-PSK and WPA2-PSK). WPA is the current encryption standard for wireless networks. It is strongly recommended that WEP not be used as the sole mechanism to secure wireless communication, due to serious weaknesses in it.

The rtwn driver can be configured at runtime with ifconfig(8) or on boot with hostname.if(5).

The driver needs at least version 1.0 of the following firmware files, which are loaded when an interface is brought up:


A prepackaged version of the firmware can be installed using fw_update(1).

The following example scans for available networks:

# ifconfig rtwn0 scan

The following hostname.if(5) example configures rtwn0 to join network “mynwid”, using WPA key “mywpakey”, obtaining an IP address using DHCP:

nwid mynwid
wpakey mywpakey

rtwn0: could not read firmware ...
For some reason, the driver was unable to read the microcode file from the filesystem. The file might be missing or corrupted.
rtwn0: device timeout
A frame dispatched to the hardware for transmission did not complete in time. The driver will reset the hardware. This should not happen.

arp(4), ifmedia(4), intro(4), netintro(4), pci(4), hostname.if(5), ifconfig(8)

The rtwn driver first appeared in OpenBSD 5.8.

The rtwn driver was written by Stefan Sperling <>. It was based on the urtwn(4) driver written by Damien Bergamini <>.

The rtwn driver does not support any of the 802.11n capabilities offered by the adapters. Additional work is required in ieee80211(9) before those features can be supported.
July 9, 2015 OpenBSD-6.1