Asus RT-AC68U and Android Modem

Hello. I want use my Android smartphone (Modem-Mode) as backup WAN on USB 2.0 router port.

Router firmware - Merlin 378.56 (kernel 2.6.36.4brcmarm).
Phone - Highscreen Boost, Android 4.1.2 (kernel 3.4.0)

I activate "Modem mode" after USB-connect, but mobile device not apper in router interface.

When i connect smartphone to PC and activate modem-mode in smartphone, PC's NetworkManager (Linux Fedora 21) configured modem correctly.

How to use android 's devices in modem-mode as backup WAN...

Asus RT-AC68U and Android Modem