USB tethering of an AT&T AirCard 815s mobile hotspot (Netgear 815s) to DD-WRT for WAN ?

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gtippitt
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USB tethering of an AT&T AirCard 815s mobile hotspot (Netgear 815s) to DD-WRT for WAN ?
I'm posting my question in the forum rather than the one for the r7800 router I'm using, because it should be the same matter on any of the routers with a USB port. and running DD-WRT.  I’m sorry if my question is addressed elsewhere, but I’ve searched for 2 days without finding a solution that works.   I’m also sorry that I’m long winded in this post, but I wanted to explain why I need USB tethering for this setup, instead of using WiFi alternatives that I already have working.
 
I am trying to get a Netgear 815s,  AT&T mobile hotspot using USB tethering to work as the WAN connection for a Netgear Nighthawk X4S AC2600/r7800 model router.  I’ve flashed the r7800 router with the V3.0-r34330M kongat (01/02/2018) version of KONG’s DD-WRT firmware.  I’ve used DD-WRT for many years extending WiFi in my house and those of friends, so I easily got these two working where the 815s hotspot is the main router and the r7800 is the client extender.  My problem is that I for the build I’m trying to set up, I really need a wired USB connection where the DD-WRT on the r7800 will be the main NAT router and using the 815s hotspot as its WAN connection for Internet access.  I found a thread at the link below where one user said it worked for them, but their config example isn’t working for me.  I don’t know if it’s because I’m using a different version of DD-WRT,  if AT&T has changed their firmware in the 815s hotspot, or if I’m missing some other needed config setting the person didn’t include in his example.
 
 
After my initial failed attempt with the USB tethering, I’ve now got it working as I have my home routers, where I have a range extending router set to use the 5GHz band as a WPS Station.  This lets both routers to provide AP at full speed on 2.4GHz.  For setups without Apple devices that don’t need 5GHZ WiFi otherwise,  using the 5GHz band for the connection between routers works really well.  Before I got routers with 5GHz, a similar setup using only 2.5GHz dramatically reduced my WiFi performance.
 
For many reasons in addition to the USB 3.0 speed, the setup I’m configuring now for a friend will work much better if I can get the USB tether to work.  He now uses lots of these AT&T hotspots for his business where he has people around the country that don’t work in the main office.  Often they are in  locations that have lots of other WiFi networks very close that cause WiFi band conflicts.  This is a annoyance with one person with a laptop, which can be overcome by connecting the hotspot to to the laptop using USB, which automatically configures everything itself with a Windows laptop.  He’s now got a new project where there will be 3 or 4 people with laptops, printers, and devices working in small LAN, so he’s adding the the r7800 router with DD-WRT to the mix.  The r7800 will have an eSATA solid state drive and function as a file server, web server, and printer server, in addition to basic NAT  router and WiFi functions
 
Using a wired USB connection between the hotspot and the DD-WRT router will make them much easier for the remote users to set up.  He needs to be able to ship them to people that can simple plug them in and work, without those people having to know how to do any DD-WRT config of WiFi or anything else.  They shouldn’t need to know more than how to plug in Ethernet and power cables, and connect the laptops to the router’s WiFi SSID if needed.   The 815s hotspot has a config option to have it turn off its WiFi automatically whenever it’s USB tethered, which will help the  r7800 router’s WiFi work better with less chance of band conflicts.  They will be connecting laptops, tablets, phones, and printers to the r7800 using both wired Ethernet and WiFi.  Ideally, the DD-WRT router will only require that they plug in its power cord and the USB cable to one of the 815s hotspots they already have and normally use with their laptops.
 
 
If I can get the 815s with USB as the WAN,  the r7800 with DD-WRT provides better security and functionality for things like DDNS, firewall, and VPN server and client tunneling to other sites.  If I must use WiFi to connect the hotspot to the r7800 DD-WRT router, then the small 815s hotspot will be the main NAT router for the LAN, and its stock firmware doesn’t provide nearly the capabilities of DD-WRT on the r7800.  The reasons for needing USB tethering versus connecting as I’ve got them so far using 5GHz, are the same as when I learned years ago for my home that I should set my ISP’s device in bridged mode so that my DD-WRT devices could play well together.
 
I’d like to give a shout out to all of the developers who have worked on DD-WRT to applaud all of their work.  I began working on enterprise network administration more than 30 years ago.  It almost seems like science fiction when I think how this router running DD-WRT does everything and more than what a small room full of equipment that was required in 1999.  Even more amazing to me than the reduction in size, power requirements, and cost of the hardware needed, is that DD-WRT makes it possible to configure all of this functionality using a simple web interface.  Even though I’ve spent 2 days trying unsuccessfully to get the USB tethering to work, I had it doing 95% of what my friend needed in less than hour after the postman delivered the hardware, including finding the latest DD-WRT firmware and flashing the router. 
 
If anyone has one of these Netgear 815s mobile hotspots with AT&T service working with USB tethering as the WAN connection for a DD-WRT router, I’d deeply appreciate any insight and assistance you can provide to me.  I’d offer to name my first child after anyone who can help, but I’m old, single, and don’t plan to have kids, so it will have to be my next dog instead.  
 
Greg
gtippitt
gtippitt's picture
I now have USB tethering to
USB tethering to the AT&T 815s Aircard mobile data hotspot to a Netgear Nighthawk AC2600/r7800 running DD-WRT is working for me now.  This hotspot uses fairly common protocols, so these instructions should work for many similar devices.  When it was not working before, I had been using the DD-WRT firmware I downloaded from the DD-WRT.com beta downloads, which are missing 3 modules, usbnet.ko, cdc_ether.ko, and rndis_host.ko.  After I loaded KONG's build of the firmware, which has these modules, from the link below, it now works as I wanted.  If these missing modules are included in future firmware builds, the commands below for the router's startup script should work for other versions.
 
 
Several old threads in DD-WRT forums, documented the commands needed for the router's startup script, before the required modules were removed from the current builds of the firmware.  I hope these modules will be added back to future builds for download one DD-WRT.com, since KONG doesn't have firmware builds for some of the routers that are available on the DD-WRT.com website.
 
For users that want to avoid using Telnet and SSH for using DD-WRT's Linux command line interface, it is easy to create a startup script using DD-WRT's Administration=>Commands menu.  You need to have the lines below in the startup script.  I added a sleep command between the other commands to ensure one command finished before the next.  This is probably unneeded with the r7800's fast CPU, but longer waits might be needed on older slower routers. Entering these commands in the command window and running them once will let you know they work correctly.  When they run during the router startup, you might not be aware of errors, but running them first on this menu will ensure you have not mistyped anything. Even if you run the commands without getting any errors.  These commands need to be run each time the router is booted, so they have to be put into the startup script.
 
  insmod usbnet
  sleep 2
  insmod cdc_ether
  sleep 2
  insmod rndis_host
  sleep 2
  ifconfig eth2 up
  sleep 2
  udhcpc -i eth2
  sleep 2
 
If you get an error that a module is not found, and you've typed it correctly, you can check to see if your router's firmware includes them by listing the modules under /lib/modules.  If you are not familiar with Linux, the ls command is used instead of Window's dir command.  First you type "ls /lib/modules" that will show you the directory named for the version of the kernel being used.  Then you type "ls /lib/modules/???/usb*, substituting the name shown from the first ls command for the ???.  From the list of USB modules displayed, see if the 3 being loaded by the insmod command are found.  As I said at the top of this post, the version of the firmware I originally download from the DD-WRT.COM Beta downloads did not include these modules, but the one I got from Kong's site did include them.  Hopefully this problem with the ones using the 4x Linux kernel on DD-WRT.com will be updated soon, especially for routers for which Kong doesn't have firmware available.
 
Once you have rebooted the router, you need to make this device the default for the router's WAN connection by going to the Setup=>Networking menu. For Port Setup - WAN Port Assignment, select eth2 from the pulldown menu.  If eth2 is not available as a choice, then DD-WRT is not accessing the hotspot correctly.  This option in the config menus replaces a prior setting that was used in some older post that set NVRAM variables for the WAN connection.
 
I am setting this router up with the hotspot for a friend to use for his business when he needs to set up a small LANs at a temporary locations.  As well as providing Internet access for devices, the DD-WRT router will also be used as a file sharing and web server for a network of a few laptops, tablets, phones, and printers.  I've tried to included the details that a user without networking knowledge can use this.  I'm not repeating the basics of flashing the router and such, since they are done well elsewhere.  I wanted to post these details especially for people who live in rural areas where they cannot get high speed wired broadband and are interested in using a device like this for their home network or small business.  I'm not promoting AT&T's service, it was just the one my friend already used.  The unlimited mobile data plans for one of these devices are comparable in cost to wired broadband.  Even though slower than wired broadband, and the speeds decrease further after some cap limit, it is still a very usable option for homes and small businesses where wired broadband isn't available. (full disclosure - I've been using the Internet since a 9600kps modem was considered fast, so anything above 56kps still seems fast to me.) For users that have cellphone service, it is definitely a great alternative to satellite Internet service.  Not matter what hardware they try for satellite Internet, they cannot solve the problem that it take time for signals to travel into orbit and back, so they have huge latency problems that reduce the real effective speeds of those services.
 
Using one of these mobile data hotspot with DD-WRT router with a USB port will let users share the hotspot's Internet service with all of the LAN's devices, wired Ethernet or WiFi.  When you tether it using USB, the hotspot's default setting is to disable its WiFi, which prevents it from interfering with the DD-WRT router for WiFi channels.  A real router can provide much better WiFi coverage and speed than the small hotspot or a cellphone sharing its data service via WiFi.  An analogy for novices, is that it is equivalent to the difference between connecting your phone to external amplified speakers for music compared to your phone's internal speaker at max volume. 
 
For a small business, one of these mobile data hotspots can also work easily as a backup for their wired broadband service.  The commands in the startup script required to enable the USB connection as the router's WAN connection, can be commented out with a # at the start of each line, so they didn't normally do anything.  When your wired Internet service goes down, you could plug the hotspot into a USB port on the router, remove the # from the beginning of the commands in the startup script, and then reboot the router and change the WAN port in the Setup-Network menu.  In just a few minutes, you'd have Internet service working again while you wait for the cable guy to show up sometime between the hours of Monday AM until Friday PM (or maybe on Wednesday of next week if you're using my ISP).  Someone could probably write a short script to run using the router's CRON facility to check the wired WAN connection periodically and automatically switch between the two connections depending upon whether the wired connections was up or down.
 
Greg
Fischwrap
Fischwrap's picture
Thanks for the info! I have

Thanks for the info! I have the same setup (hotspot and router models) but I can't get this to work for the life of me. 

I'm on the ddwrt build from here:

http://www.desipro.de/ddwrt/K3-AC-IPQ806X/

The three modules aren't showing. I see usbnet.ko, but neither cdc_ether.ko or rndis_host.ko. I'm pretty sure I've successfully added the startup script (copy-pasted into the box, and hit 'save startup', and it shows in the startup box), but I suspect without these two modules, I won't be able to operate the router this way. Any insight you could offer would be much appreciated!