Media for Load-balancing across four T1's on 2 routers

Load-balancing across four T1's on 2 routers

I am setting up the following:

- 2 Cisco 2800 series routers, each has two T-1 internet connections.

- Those 2 routers are also connected to a 100mb layer-3 switch.

- Our firewall will also connected to that layer-3 switch.

- The firewall's' default gateway will be that layer-3 switch.

- The workstations are behind the firewall, and will use the firewall as their default gateway

- OSPF will be running on the 2 routers and the layer-3 switch, and also on 2 routers on the ISP's site.

- The OSPF area will be Totally Stubby, thus the ISP's routers will be advertising default routes into our network.

As long as all four T-1's are up, everything should work fine:

- The workstations will route outbound packets to the firewall

- The firewall will route the packets to the layer-3 switch

- The layer-3 switch is running OSPF and will see two equal cost default routes, and will load-balance traffic between our two routers

- The routers will in turn also have two defaults routes (1 route through each T-1), and load-balance traffic across each T-1

My problem is what happens when one T-1 goes down? Our layer-3 switch will still see equal cost routes and split the traffic across the two routers, even though one router has 1/2 the bandwidth.

Can someone help me with this problem? Please let me know if you have any questions on what I explained above! Here is a diagram of the setup, i hope it looks ok:

R1 R2 (ISP Routers) || || || || (4 total T-1s) || || R1 R2 (Our Routers) | | \ / \ / \ / Layer-3 Switch | | | Firewall | | | Layer-2 Switch | | | | Workstations

Thanks! Sean