2 internet connections. If one drops, how to auto-switch to the other?

[sugi123]

I have two internet connections, one Optimum online, and another, an optimum wifi connection, two separate internet connections. Both are connected to my dual-NIC motherboard (feeds in through 2 routers with DD-WRT setup as client bridges). My question is, if one of them drops connection (but still there is a valid IP, but no internet), how can I make it so that it automatically switches to the other for internet traffic? thanks.

 

[JustAGuy51]

Assign a metric to each connection, one preferred than the other. When one drops, the backup connection will become preferred connection.