I have a Cisco 2801 connected to a Sprint MPLS network. For a backup, we had a cheap Internet T1 installed and planned on setting up an IPSec tunnel back to the datacenter.
Our vendor sold us a Covad Internet T1 which setups up differently than what I am used to. They use a Frame Relay PVC and issue IP information via PPP IPCP. I had it all setup and the circuit came up, but I soon realized the PPP IPCP DEFAULT ROUTE command ended up replacing the default route my router learned from the MPLS network. I removed PPP IPCP DEFAULT ROUTE from the Virtual-Template and bounced the serial interface, and it appears to have come back up, but I am unable to route any traffic out.
I tried adding a static route pointing to the serial subinterface, but when I issue the SHOW ROUTE command for the route I added, the router reports the subnet doesn't exist in the routing table. It doesn't appear I can add a route out a Virtual-Access interface either.
How can I make this work?
I suppose that the backup T1 connection is using a stable IP address at the ISP's end. This IP address will appear in your routing table having the mask /32, i.e. a host route - this is also a part of the IPCP negotiation between you and your ISP. If this IP address is stable indeed then you can define a static default route using this particular IP address as the next hop (without referring to the outgoing interface because that is dynamic) and having the administrative distance higher than 110.
Can you try this to see if it works for you?