I currently manage several office locations which each have two internet connections, a DSL line and some bonded T1 lines. Currently, the DSL line is used for the internet and the bonded T1 lines are used for site-to-site IPSEC VPN tunnels for the internal network. This is all handled by Cisco 2800 series routers at each location which handle the VPN tunnels and splitting the traffic between the DSL lines and T1 lines.
The T1 site-to-site VPN tunnels are going to be replaced by a MPLS network. The MPLS provider is going to provide CISCO 1841 routers to act as the gateway, which my 2800s will connect to. I am going to keep the DSL lines for internet traffic. So my 2800 will connect to both the DSL line and the MPLS network.
Is there a way I could set up 2800s to use the VPN tunnels going over the DSL lines as a fail over for internal traffic if the lines go down. Or, even better, is there a way I could those VPN tunnels going over the DSL lines to fail over if the MPLS line goes down or if the MPLS line's bandwidth is currently maxed out? What would that entail?