1. Client Mode

If you want to use OpenWrt to connect your router to another access point (AP) or computer rather than run it as an AP itself, follow these steps.

Reading the Setting up OpenWrt in client mode thread in the forum might help your understanding of Client Mode a bit.

NOTE: the instructions in this howto reference the nvram command. This applies to the WhiteRussian releases of openwrt. Kamikaze abandons nvram in favor of files in /etc/config/ (/etc/config/network and /etc/config/wireless, at a minimum). Refer to the ClientModeKamikazeStyleHowto

1.1. Requirements

You need to have a recent version of OpenWrt White Russian (at least RC3) installed
A Wrt router (which acts as your client)
An access point where you can connect your Wrt to

1.2. Configuring client mode

The first step would be changing the Wrt's behavior from AP to client mode.

nvram set wl0_mode=wet         # bridged client
OR
nvram set wl0_mode=sta         # routed client

If you are going to leave the wireless interface bridged to the LAN on br0, then you should choose wet. If you are going to configure Wrt as a router, so that the wireless interface is a pure client and the LAN is on a completely different subnet, then choose sta.

NOTE: As soon as your AP is in client mode you can't connect any wireless clients to it anymore because it's not in AP mode (wl0_mode=ap). Also note that wl0 above is WL in lower case followed by Zero.

There are two different client modes: bridged and routed. They are mutually exclusive.

1.2.1. Bridged client mode

In bridged client mode, all computers connected to the client will be connected to the subnet of the access point you are connecting to (no firewalling, unless you use ebtables).

When using the bridged client mode, you should disable the DNS/DHCP server: If the "chmod" command fails and reports a read-only file system you will have to remove it instead (you can always put it back since it's just a symlink to the real script).

chmod -x /etc/init.d/S50dnsmasq
OR
rm /etc/init.d/S50dnsmasq

If your configuration was previously set to "routed" client mode, you'll need to add the wireless interface to the bridge again and remove it from the wan interface. See OpenWrtDocs/NetworkInterfaces for more information.

$/!\$ IMPORTANT: Use the correct network interface names for your hardware version.

nvram set lan_ifnames="vlan0 eth1"
nvram set wan_ifname=vlan1

1.2.2. Routed client mode

Routed client mode breaks down the default bridge between the wireless interface and the LAN ports. Note that we are using the wan_ifname to refer to the wireless connection; this will save you from having to change the firewall script.

$/!\$ IMPORTANT: Use the correct network interface names for your hardware version.

nvram set lan_ifname=br0
nvram set lan_ifnames=vlan0
nvram set wan_ifname=eth1         # the wireless interface

Then configure the interfaces normally. Be sure not to use the same subnet for lan and wlan. For example, assuming the wifi interface uses DHCP and the LAN interface is choosen to have the static IP address 192.168.2.1:

nvram set lan_ipaddr=192.168.2.1
nvram set lan_proto=static
nvram set wan_proto=dhcp

You can configure other options if you need to, like wan_dns or wan_gateway.

When you are done with setting up the NVRAM, just commit and reboot:

nvram commit
reboot

Note: The Asus WL-HDD (and possibly other units without built-in switch) will not be able to be configured as a router (client or otherwise) with default OpenWrt firmware(using RC4). This is due to the /etc/init.d/S05nvram startup script that checks the unit type and configures two necessary parameters back to settings for bridge mode. Searching the script for "WLHDD" and commenting out that particular case will allow your settings to remain after next reboot, and thus allow the unit to be configured as a router.

1.3. Finding and joining networks

You can now scan for nearby access points. If iwlist doesn't find any networks on the first run, repeat the scanning a few times.

TIP: With iwlist you can only scan for networks when your AP is in client mode.

root@OpenWrt:/# iwlist eth1 scanning
eth1      Scan completed :
          Cell 01 - Address: aa:bb:cc:dd:ee:ff
                    ESSID:"OpenWrt"
                    Channel:1
                    Quality:0/0  Signal level:-17 dBm  Noise level:-92 dBm
                    Bit Rate:1 Mb/s
                    Bit Rate:2 Mb/s
                    Bit Rate:5.5 Mb/s
                    Bit Rate:11 Mb/s
                    Bit Rate:18 Mb/s
                    Bit Rate:24 Mb/s
                    Bit Rate:36 Mb/s
                    Bit Rate:54 Mb/s
                    Bit Rate:6 Mb/s
                    Bit Rate:9 Mb/s
                    Bit Rate:12 Mb/s
                    Bit Rate:48 Mb/s
root@OpenWrt:/#

To join a non-encrypted access point run these commands:

ifdown wan
nvram set wl0_ssid=<SSID>
nvram set wl0_channel=<CHANNEL_NUMBER>
ifup wan; /sbin/wifi

You can configure encryption like WEP or WPA the way you would if the device was in access point mode. For example, using WEP;

ifdown wan
nvram set wl0_ssid=<SSID>
nvram set wl0_channel=<CHANNEL_NUMBER>
nvram set wl0_wep=enabled
nvram set wl0_key=1
nvram set wl0_key1=<WEP key in hex format>
ifup wan; /sbin/wifi

If you use WPA you can find the relevant configuration options under OpenWrtDocs/Configuration.

Don't forget to commit if you want your settings to survive a reboot:

nvram commit

NOTE: WPA2 in client mode is broken in RC4 and RC5. On the Wireless Configuration page of the web interface, disable the WPA2 checkbox. WPA1 and WEP still work properly in RC4 and RC5.

1.4. Some more configuration

When you set an interface to DHCP, OpenWrt runs the DHCP client on that interface automatically at boot time. If you want to re-run the dhcp client, for example because you joined another network, you can either reboot, or you can run the ifup command:

ifup wan; /sbin/wifi

This will set up the wireless interface according to your nvram settings.

2. Links

Detailed information on setting up a wired-wireless bridge with encryption
- WirelessBridgeWithWPAHowto

CategoryHowTo