Use NCM USB Dongle for WAN connection

NCM (Network Control Model) is Ethernet over USB protocol used by some fast speed USB modems/dongles.

For more information about other protocols commonly used:

You may need to switch your modem to provide a native NCM interface instead of serial Modem interface.

:!: Please read about AT commands for your modem.

Once you've done - you can disconnect modem from the PC and connect it to the router.

1. Install OpenWrt

2. Complete steps OpenWrt Configuration

Router should be turned on and connected to the Internet to get the needed packages. Please refer to: Internet Connection.

To make use of NCM protocol, packages kmod-usb-net-huawei-cdc-ncm and comgt-ncm are needed.

To access the PC UI Interface (AT Command port) package kmod-usb-serial-option is typically needed.

1. Install usb-modeswitch if that is needed for switching the modem into a “working” state. More about: USB mode switch

2. A terminal program like picocom will be needed to manually send AT commands.

3. Add support for FlashCard of your dongle - refer to: USB Storage

1. Install all the needed packages

opkg update
opkg install kmod-usb-net-huawei-cdc-ncm luci-proto-ncm picocom

Other modules will be automatically installed as dependencies.

:!: If your have not enough space on your device - think of installing Rootfs on External Storage (extroot)

:!: Another option is Hardware memory upgrade. Refer to your router Forum thread for possibility and instructions.

2. Reboot the router


3. Check that everything is OK and you got new device:

ls -l /dev/cdc-wdm0

crw-r--r--    1 root     root      180, 176 Oct  1 12:03 /dev/cdc-wdm0

If you have no such device - try to find out what went wrong:

try dmesg to read kernel logs on USB init


or look info about USB devices and interfaces present in the system:

cat /sys/kernel/debug/usb/devices

T:  Bus=03 Lev=01 Prnt=01 Port=00 Cnt=01 Dev#=  2 Spd=480  MxCh= 0
D:  Ver= 2.10 Cls=00(>ifc ) Sub=00 Prot=00 MxPS=64 #Cfgs=  1
P:  Vendor=12d1 ProdID=1506 Rev= 1.02
S:  Manufacturer=HUAWEI_MOBILE
C:* #Ifs= 5 Cfg#= 1 Atr=80 MxPwr=  2mA
I:* If#= 0 Alt= 0 #EPs= 3 Cls=ff(vend.) Sub=03 Prot=10 Driver=(none)
E:  Ad=82(I) Atr=03(Int.) MxPS=  10 Ivl=32ms
E:  Ad=81(I) Atr=02(Bulk) MxPS= 512 Ivl=0ms
E:  Ad=01(O) Atr=02(Bulk) MxPS= 512 Ivl=0ms
I:* If#= 1 Alt= 0 #EPs= 2 Cls=ff(vend.) Sub=03 Prot=12 Driver=option
E:  Ad=83(I) Atr=02(Bulk) MxPS= 512 Ivl=0ms
E:  Ad=02(O) Atr=02(Bulk) MxPS= 512 Ivl=0ms
I:  If#= 2 Alt= 0 #EPs= 1 Cls=ff(vend.) Sub=03 Prot=16 Driver=huawei_cdc_ncm
E:  Ad=85(I) Atr=03(Int.) MxPS=  16 Ivl=2ms
I:* If#= 2 Alt= 1 #EPs= 3 Cls=ff(vend.) Sub=03 Prot=16 Driver=huawei_cdc_ncm
E:  Ad=85(I) Atr=03(Int.) MxPS=  16 Ivl=2ms
E:  Ad=84(I) Atr=02(Bulk) MxPS= 512 Ivl=0ms
E:  Ad=03(O) Atr=02(Bulk) MxPS= 512 Ivl=0ms
I:* If#= 3 Alt= 0 #EPs= 2 Cls=08(stor.) Sub=06 Prot=50 Driver=usb-storage
E:  Ad=86(I) Atr=02(Bulk) MxPS= 512 Ivl=0ms
E:  Ad=04(O) Atr=02(Bulk) MxPS= 512 Ivl=125us
I:* If#= 4 Alt= 0 #EPs= 2 Cls=08(stor.) Sub=06 Prot=50 Driver=usb-storage
E:  Ad=87(I) Atr=02(Bulk) MxPS= 512 Ivl=0ms
E:  Ad=05(O) Atr=02(Bulk) MxPS= 512 Ivl=125us


See Troubleshooting Section of this page for more information.

UCI is supporting NCM network protocol configuration.

Name Type Required Default Description
device file path yes (none) NCM device node, typically /dev/cdc-wdm# or /dev/ttyUSB#
apn string yes (none) Used APN
pincode number no (none) PIN code to unlock SIM card
username string no (none) Username for PAP/CHAP authentication
password string no (none) Password for PAP/CHAP authentication
auth string no (none) Authentication type: pap, chap, both, none
mode string no (modem default) Used network mode, not every device support every mode: preferlte, preferumts, lte, umts, gsm, auto
pdptype string no IP Used IP-stack mode, IP (for IPv4), IPV6 (for IPv6) or IPV4V6 (for dual-stack)
delay number no 0 Seconds to wait before trying to interact with the modem (some modems require up to 30 s.)
profile number no 1 Index of a PDP context

You can configure UCI manually using uci command line or text editor or with Luci package luci-proto-ncm.

:!: If option “mode” is set, the corresponding AT command is sent to the modem on every connection attempt. Most of modems (at least all Huawei models) store this setting in internal flash. So on each connection OpenWrt writes to modem flash. It is recommended to not use this option after the required mode is set once.

Using Luci web interface: navigate to Network → Interfaces → Add new interface… → Protocol : NCM, Interface: “ttyUSB1”

The interface selected above is the “AT Command Port” or “PCUI” in Huawei terms, ttyUSB1 is shown as an example only, different modems have different port assignments. The data interface like /dev/cdc-wdm0 will be discovered by the connection script automatically.

Enter your APN and select the 'IP Protocol' as instructed by the carrier.

Assign the firewall zone (wan) on 'Firewall Settings' tab.

Alternatively you can edit the configuration files with any text editor like vi or nano:

  • add a new Interface in /etc/config/network:
config interface 'wwan'
        option proto 'ncm'
        option device '/dev/ttyUSB1'
        option pdptype 'IP'
        option apn 'internet'
  • add the same interface name to the “wan” firewall zone in /etc/config/firewall:
config zone
    option name 'wan'
    list network 'wwan'

Some providers of the cellular internet use redirection to their pages for access activation, when you are connected first time. I.e. YOTA in Russia.

Normally this would be blocked by dnsmasq:

Jan 18 14:36:49 OpenWrt daemon.warn dnsmasq[1325]: possible DNS-rebind attack detected:

You have 2 options:

  • Allow rebind responses RFC1918 (In LUCI goto NetworkDHCP and DNS and uncheck Rebind protection checkmark)
  • Add domain to Whitelist (In LUCI goto NetworkDHCP and DNS and type in “” without quotes to the Domain whitelist field.

Save & apply

Get the information about USB devices with cat /sys/kernel/debug/usb/devices

Find a section for your device, look for “Manufacturer” and/or “Product” lines corresponding to your modem, for example:

S:  Manufacturer=HUAWEI_MOBILE

See if necessary drivers are loaded for your device:

I:* If#= 1 Alt= 0 #EPs= 2 Cls=ff(vend.) Sub=03 Prot=12 Driver=option
I:  If#= 2 Alt= 0 #EPs= 1 Cls=ff(vend.) Sub=03 Prot=16 Driver=huawei_cdc_ncm

If the drivers are missing, install the missing packages and/or change the operating mode of the modem to expose the necessary interfaces.

Finally, ask in the forum.

This script GitHub oilervoss will check the connection pinging a public IP and, under failure, it will send AT commands to the serial interface of the modem restarting it.

To achieve continuous monitoring of the connection, it must be called recurrently through a cron job as:

#min    h   day  mon  week  command
*/20    *    *    *    *    /etc/init.d/ncm-fix start

This is probably related to ticket #18673 ( You should be able to use the modem by starting ndis manually by sending the following to /dev/ttyUSB1


It is possible to automate this task using hotplug. Below are some scripts fetched from Do not forget to modify them to your needs. The scripts are for Huawei modems obviously.


#!/bin/sh /etc/rc.common

# Interface name from /etc/config/network
# Your APN:


start() {
        if [ -e ${DEVICE} ]; then
                echo -ne "AT^NDISDUP=1,0\r\n" > ${DEVICE}
                sleep 3
                echo -ne "AT^NDISDUP=1,1,\"${APN}\"\r\n" > ${DEVICE}
                sleep 3
                ifup $IFNAME
                echo "No such device ${DEVICE}" | logger -t "ncm-network[$$]" -p info

stop() {
        if [ -e ${DEVICE} ]; then
                ifdown $IFNAME
                sleep 3
                echo -ne "AT^NDISDUP=1,0\r\n" > ${DEVICE}
                echo "No such device ${DEVICE}" | logger -t "ncm-network[$$]" -p info



# Uncomment set line below and check your modalias I from tmp file

#set >> /tmp/ncm-network.debug

if [ "${MODALIAS}" != "${MODEM_ID}" ]; then
        exit 0

case "$ACTION" in
                SYSTEM_UPTIME=$(cat /proc/uptime | awk -F"\." '{ print $1 }')
                if [ "${SYSTEM_UPTIME}" -gt 60 ]; then
                sleep ${PAUSE} && \
                echo "Start modem ${MODEM_ID}" | logger -t "hotplug[$$]" -p info && \
                /etc/init.d/ncm-network start
                } &
                echo "Stop modem ${MODEM_ID}" | logger -t "hotplug[$$]" -p info
                /etc/init.d/ncm-network stop

Some modems does not reconnect after losing connection. Here is a connection check sh script which checks if it can ping remote servers with time intervals. If all pings fail, it tries to start the network by executing /etc/init.d/ncm-network start


# Enter the FQDNs you want to check with ping (space separated)
# Script does nothing if any tries to any FQDN succeeds

# Sleep between ping checks of a FQDN (seconds between pings)
SLEEP=3                         # Sleep time between each retry
RETRY=3                         # Retry each FQDN $RETRY times
SLEEP_MAIN=60                   # Main loop sleep time

  for NAME in $FQDN; do
    for i in $(seq 1 $RETRY); do
      ping -c 1 $NAME > /dev/null 2>&1
      if [ $? -eq 0 ]; then
        return 0
      sleep $SLEEP
  # If we are here, it means all failed
  return 1

while true; do
  if [ $? -ne 0 ]; then
    /etc/init.d/ncm-network start
  sleep $SLEEP_MAIN

If your SIM receives a voice call. It will downgrade to CS network which means you will downgrade into 3G mode. To avoid this, set the stick to use only PS network by creating `/etc/hotplug.d/iface/99-ifupwwan` file with following code. Make sure to modify it to use correct serial interface and correct AT command for your device.

[ "$ACTION" = "ifup" -a "$INTERFACE" = "wwan" ] && {
    logger "iface wwan up detected..."
    # We need to set this to stop the card from receiving phone calls
    # This is for EC-25
    #echo -ne "\r\nAT+QCFG=\"servicedomain\",1,1\r\n" > /dev/ttyUSB2
    # This is for Huawei
    echo -ne "\r\nAT^SYSCFGEX=\"00\",3FFFFFFF,1,1,7FFFFFFFFFFFFFFF,,\r\n" > /dev/ttyUSB2
This website uses cookies. By using the website, you agree with storing cookies on your computer. Also you acknowledge that you have read and understand our Privacy Policy. If you do not agree leave the website.More information about cookies
  • Last modified: 2024/03/30 13:06
  • by andrewz