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

.

Relevant Pages

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