---
name: "rsu"
section: "4"
platform: "openbsd"
package: "man"
version: "8.0-current-20261101"
release: "OpenBSD 8.0-current (2026-11-01)"
platforms: ["freebsd", "openbsd"]
url: "https://new.carta.tech/rsu"
---

# rsu(4)

Realtek RTL8188SU/RTL8192SU USB IEEE 802.11b/g/n wireless network device

## NAME

**rsu** – Realtek RTL8188SU/RTL8192SU USB IEEE 802.11b/g/n wireless network device

## SYNOPSIS

**rsu\* at uhub? port ?**

## DESCRIPTION

The **rsu** driver supports USB 2.0 wireless network devices based on Realtek RTL8188SU, RTL8191SU and RTL8192SU chipsets.

The RTL8188SU 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.

The RTL8191SU is a highly integrated multiple-in, single-out (MISO) 802.11n adapter that combines a MAC, a 1T2R capable baseband and an RF in a single chip. It operates in the 2GHz spectrum only.

The RTL8192SU is a highly integrated multiple-in, multiple-out (MIMO) 802.11n adapter that combines a MAC, a 2T2R capable baseband and an RF in a single chip. It operates in the 2GHz spectrum only.

These are the modes the **rsu** 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.

The **rsu** driver can be configured to use Wired Equivalent Privacy (WEP) or Wi-Fi Protected Access (WPA1 and WPA2). WPA2 is currently the most secure encryption standard for wireless networks supported by OpenBSD. It is strongly recommended that neither WEP nor WPA1 are used as the sole mechanism to secure wireless communication, due to serious weaknesses. WPA1 is disabled by default and may be enabled using the option "**wpaprotos** *wpa1,wpa2*". For standard WPA networks which use pre-shared keys (PSK), keys are configured using the "**wpakey**" option. WPA-Enterprise networks require use of the wpa\_supplicant package.

The **rsu** driver can be configured at runtime with [ifconfig(8)](/ifconfig/8.md) or on boot with [hostname.if(5)](/hostname.if/5.md).

## FILES

The adapter needs firmware files to run, which are loaded on demand by the driver when the device is attached:

- */etc/firmware/rsu-rtl8712*

  ## HARDWARE

The following adapters should work:

- ASUS USB-N10

  - ASUS WL-167G V3

  - Belkin F7D1101 v1

  - D-Link DWA-131 A1

  - Hercules HWGUn-54

  - Hercules HWNUm-300

  - Planex GW-USNano

  - Sitecom WL-349 v1

  - Sitecom WL-353

  - Sweex LW154

  - TRENDnet TEW-648UB

  - TRENDnet TEW-649UB

  ## EXAMPLES

The following example scans for available networks:

```
# ifconfig rsu0 scan
```

The following [hostname.if(5)](/hostname.if/5.md) example configures rsu0 to join network “mynwid”, using WPA key “mywpakey”, obtaining an IP address using DHCP:

```
join mynwid wpakey mywpakey
inet autoconf
```

## DIAGNOSTICS

- rsu0: error N, 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.

- rsu0: 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.

## SEE ALSO

[arp(4)](/arp/4.md), [ifmedia(4)](/ifmedia/4.md), [intro(4)](/intro/4.md), [netintro(4)](/netintro/4.md), [usb(4)](/usb/4.md), [hostname.if(5)](/hostname.if/5.md), [ifconfig(8)](/ifconfig/8.md)

## HISTORY

The **rsu** driver first appeared in OpenBSD 4.9.

## AUTHORS

The **rsu** driver was written by Damien Bergamini ⟨*damien.bergamini@free.fr*⟩.

## CAVEATS

The **rsu** driver does not support any of the 802.11n capabilities offered by the adapters. Additional work is required in [ieee80211(9)](/ieee80211/9.md) before those features can be supported.