We have two ISP links and second one is using for back-up purpose in case first link goes down then all internet traffic moves over the second link and while primary link come back functional then the traffic moves back as previously.
The STS Tunnel is configured and around 10 production sites are connected with first ISP link and when primary link works then only tunnel traffic can be move and remote sites are accessible but in-case the primary link goes down then the internet works fine as firewall replace the route of internet traffic. I have tried to configure the STS VPN connection to test the VPN traffic to be moved on the backup link if primary ISP goes down but I am not being succeed. I am following the same STS Tunnel configuration as same configured for the primary ISP.
Can anyone suggest what settings are required so that the VPN traffic also works in case of failure of primary link.