redundant internet connection with failover
I have a Red hat linux 8 machine configured as a router. The server has 3 interfaces eth0, eth1 and a dial up modem connection. eth0 is connected to the local lan. A cable modem is connected to eth1 and the dial up connection is used as a backup. The default connection to internet is via cable modem and if this goes down the dial up interfaced is used manually to connect to the internet.
I want a permanent connection to the internet. The cable modem interface is the default interface to internet and if this goes down only then dial up interface should be up. When the dial up interface is up and the cable modem becomes usable, the dial up interface should be disconnected.
I want a solution for this which should do all the above things automatically without manual intervention.
Thanks in advance