Cellular Phone/USB Modem as WAN connection

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Main Guide [Updated 3/2020]

USB Tethering with an Android phone, or using a USB Modem, on your DD-WRT-enabled router.

USB Phone Tethering [Attach a phone via USB to a router]

Tethering your DD-WRT router to an Android phone?

Here is a Step-by-Step, with a $40/m unlimited plan and a $5 router

Phone: Verizon Visible R2 (ZTE) $19 phone with a $40/m completely unlimited LTE-only pre-pay
Router: Linksys EA6400 running DD-WRT v3.0-r37012 std (2018/09/21) and also works with r42819 (2020/03/30)

1. This assumes you have reset your router FIRST. If you have an existing custom config, back it up, then reset the router, and test this out. If you can get it working from a reset router, then you'll have to figure out what you need to do after reloading your custom config if it does not work.

2. This also assumes that the build you downloaded and flashed of DD-WRT, has the modules cdc_ether.ko and rndis_host.ko If it does not, you may need either: a larger version of DD-WRT that includes them, or to reflash over to OpenWRT. They are -very small- modules (8kb) but are not included on some larger builds for some routers. Noobs: These instructions walk you through how to figure out if the modules exist.


  1. Phone: connect to router's USB port
  2. Turn on your phone's Developer Options: [Click 'Build Number' in 'About Phone', 7 times in rapid succession]
  3. Search for 'Default USB Configuration' in 'Developer Options'. Set it to 'USB Tethering'
  4. Use Android's Smart Lock feature to automatically unlock your phone, or turn off your screen lock (PIN or pattern etc). The phone must be unlocked for USB Tethering to turn on automatically when the router is booting-up, the phone plugged in & powered-up from the Router USB port.
  5. Router: Services, USB: Enable 'Core USB Support'. Apply.
  6. Phone: USB Tethering will turn on automatically. Check to make sure this is happening.
  7. Telnet into the router. Run the following commands:
    1. cd /lib/modules/... where '...' is your kernel version
      The last folder, e,g, .../4.4.157, will vary in name, depending on the build of DD-WRT.
      For noobs: do a cd /lib/modules, then an ls to see what the name of the folder is. Or look in Status tab.
    2. insmod usbnet.ko
    3. insmod cdc_ether.ko
    4. insmod rndis_host.ko
      Use the command 'lsmod' to verify the modules usbnet, cdc_ether and rndis_host are running.
    5. ifconfig usb0 up
    6. udhcpc -i usb0
      You should be able to 'ping google.com' now from within the telnet interface, but not yet on any connected client devices. Noobs: CTRL-C to stop pinging.
    7. iptables --table nat --append POSTROUTING --out-interface usb0 -j MASQUERADE
    8. iptables --append FORWARD --in-interface br0 -j ACCEPT
      You should now be able to ping google.com from any client devices.

If the above works for you, then you can automate it by adding the following lines to the Startup script:
1. Go to the tab Administration, Commands.
2. Paste:
cd /lib/modules/x.x.xxx #change these values based on your kernel build
insmod usbnet.ko
insmod cdc_ether.ko
insmod rndis_host.ko
ifconfig usb0 up
udhcpc -i usb0
iptables --table nat --append POSTROUTING --out-interface usb0 -j MASQUERADE
iptables --append FORWARD --in-interface br0 -j ACCEPT

You may also need to add:

  • If you are trying to hide tethering:
iptables -t mangle -I POSTROUTING -o `get_wanface` -j TTL --ttl-set 65
iptables -t mangle -I PREROUTING -i `get_wanface` -j TTL --ttl-set 65
  • If you have problems with some websites not working correctly [MTU issues]:
iptables -t mangle -A FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-mss-to-pmtu
You may also have to specify a smaller MTU in the main router Setup page.

3. Click 'Save Startup'.

Alternatively, you could break out the iptables commands into the Firewall script. But I haven't gotten it to work (no connectivity after Applying changes). Usually, just reboot the router after making additional changes.

4. Click on (Administration) Management. Click 'Save'. Then 'Reboot Router'.

Credits: Users sydlexia and shenoyh on the forums.

See link: https://forum.dd-wrt.com/phpBB2/viewtopic.php?p=1128616#1128616

USB Modem [Use dongle that contains a SIM]

There are newer methods, integrated into the firmware than the previous version of this wiki. The relevant threads: K26 NEWD-2 Mega/Big builds starting with 14414 now have the 3G/UTMS WAN connection option built into the firmware.

See the following thread for more information:


See also http://www.dd-wrt.com/wiki/index.php/Mobile_Broadband for a list of directly supported device in K26 and K3.x builds.