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Sierra Wireless USB881 3G Modem WAN on WRTSL54GS via OpenWrt Kamikaze

As noted in a previous post National Shame: Swaths of Non-Rural US without Broadband; Time for Re-Divestiture, there is no Cable Modem service or DSL in my neighborhood. Up until a few  months ago, I did have a pretty nice point to point Dual Raido Full Duplex 802.11n connection that could do about 12Mbps symetrical. The only reason I had that link in the first place was because I had been in the wireless and ISP business and knew someone who would hook me up. Unfortunately the friend who supplied it to me had to shut down his network due to Depression 2.0.

So the only way I’ve been able to have an Internet connection at home is to use a 3G wireless modem. I had an AT&T / Sierra Wireless USB881 3G modem that my brother had given to me when I was sick. The hospital didn’t have any Internet service (and that hospital wasn’t in some 3rd world nation, it was in downtown San Francisco! More National-Shame).

Since I wanted to supply my whole house with always on connectivity I needed to hook the 3G modem to a router. And being the cheapskate / hacker I am I decided I needed to use one of the Linksys WRTSL54GS routers that happen to have USB ports on them to do it.Turned out that there isn’t too much documenation on doing this, particularly if you want to use the Web GUI that comes with OpenWrt.


The latest version of OpenWrt (Kamikaze 8.09) along with the packages that go along with it has everything needed to make the WRTSL54GS work with many of the 3G USB modems including the Sierra Wireless 881. Th WRTSL54GS is based on the Broadcom BCM47XX chipset. This determines which version of the OpenWrt firmware to download and install.

If you are installing on top of the standard Linksys firmware, you’ll want to install rom the brcm47xx directory and use the WrtSL54GS specific file: openwrt-wrtsl54gs-squashfs.bin. If you have already installed OpenWrt and want to update or start from scratch, you would go to the same brcm47xx directory and download the generic openwrt-brcm47xx-squashfs.trx file .(You’ll probably want both in case you have a problem after you install OpenWrt firmware. Note that I won’t go into how to restore the original Linksys firmware. There are instructions to do this, I never did).

Hook up your computer (Mac, Linux or Legacy Windows) to the router via ethernet to the router’s LAN port (not the WAN port). Make sure that you still have some kind of Internet connection to your computer.

If you are using the standard Linksys software, go to the firmware upgrade page of the Web GUI and load the openwrt-wrtsl54gs-squashfs.bin that you should have downloaded by now. Don’t disturb the router while it loads. Wait till the LEDs on the front panel stop blinking and then try to reconnect to the router via (If you don’t know how to do this step, forget about doing the rest of this how-to except see the note at the botom to just buy a commercial router that can do utilize 3G modems out of the box.)

At this point you should see something like:

OpenWrt Login

You can log in with any password at this point and you should see:

OpenWrt Greeting Page

Click on the “Administration” Menu Bar Item to get to the full Admin menu from where you can select on “Network” so you can activate the ethernet WAN:

Network Select

You will then want to enable the eth1 as the WAN interface so that you can plug the router into an ethernet that has an Internet connection. Once you clicked to enable wan/eth1, then click on “Save & Apply”:

Enable Eth1 WAN

Use the OpenWrt Opakgs system to download the kernel drivers for USB and package for doing PPP scripts by selecting System->Software:

Select System Software

And then click on the “Update ackage lists” link:

Update Package Lists Link

If you get “Error (Code 256), it means your router is not properly hooked up to an Internet connection on the WAN port.

I had to use my Mac in Internet Sharing mode in order to have Internet both to my Mac and to the router while setting it up since my only Internet connection was he 3G modem. To turn on Internet Sharing on the Mac (once you had the 3G Modem connected to the Mac) is to go to System Preferences-Sharing and turn on Internet Sharing:

Macintosh Internet Sharing

For some reason the Mac Internet Sharing and the OpenWrt/Linksys Ethernet WAN port would not get the Router IP Address via DHCP, so I had to manually set the router’s WAN interface IP addresses. I also had to Add DNS Server as an “Additional Field”. Here’s how I had set up the WAN / Eth1 Interface on the OpenWrt Network->Interfaces->WAN page. You probably don’t have to do this if you have the router hooked up to some other Internet source:

Enabling Internet Sharing on the Mac

Once you get the temporary Internet connection to your router going, you’ll want to select:


I also installed kmod-usb2

You do that by selecting the appropriate items:

and then scrolling to the bottom and selecting “Perform Actions:

Then reboot or power cycle the router.

Once it comes up, you can now reconfigure the router WAN port to use the 3G Modem. First go to the WAN configuration page in order to delete the old ETH1 WAN interfaces:

Network WAN Interface Select

You’ll want to delete the current WAN entry by clicking on the “Remove entry” button and then click on “Save & Apply” at the bottom of the page:

Remove WAN Entry

Then create a new WAN interface by clicking on “Add Entry”:

Add WAN Entry

Then in the new entry select UMTS/3G as the protocol

Fill in using the appropriate info for your carrier. I got my info by looking at the Macintosh System-Preferences->Network-Mini Card->Advanced:

You should now plug your 3G modem into the router. Then set the  OpenWrt Network->Interfaces->WAN page as shown below (with your own proper info for APN, Username, password and optionally PIN code), when done hit “Save & Apply”:

You probably need to reboot at this point. When it comes up, you should be working with 3G!

NOTE: For those of you who just want to have a 3G conection thru a router you are probably better off buying a CradlePoint router. You can get nice package deals from the 3GStore (I have no affiliation with them, its just the place I would probably have bought one myself).

One Comment

  1. Tibia Tibia September 4, 2010


    Thanks, I always aprisiate a good read. Dont stop posting!…

Comments are closed.