Using USB Modem or second WAN as a backup connection

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Hi,

I'm using RT-N56U_3.4.3.9-095_base (previously *-081) and I must say that this 
is the best router / firmware combination I have ever had. The *-081 worked 
flawlessly since the beginning. Thank you for your hard work.

I've switched to 095 to use the "Detect Internet" feature hoping this will 
allow me to create an automatically switched backup connection. When Internet 
is down on the WAN it switched to the mode as I expected, although it takes a 
while with a polling time 20s/5s it takes about 2 min until the modem is up.

I'm wondering if there's a way to switch back to WAN when the Internet is back. 
This is not a link down situation but just an ISP problem when the link is up 
but the Internet doesn't work anymore.

Another option would be to use a second router with the USB modem and have the 
N56U switch the deault gateway through that router when Internet is down and 
switch it back when is up.

Is it possible to do this using the custom scripts. Can I have multiple WAN 
interfaces?

Thank you,
Serban

Original issue reported on code.google.com by [email protected] on 17 Jul 2015 at 7:56