Hi,
Do you have your own IP block Public subnet? or you just have IP subnets from both ISPs.
Scenario1:
If you have your own IP subnet, then loadbalancing & redundancy could be achieved, you would need to have HSRP or GLBP on the Core facing Interface with routers and run IBGP between both routers. refer to Loadsharing with BGP (Multihoming Section).
The connectivity between both routers will also introduce redundancy if one of the WAN fails in order to reroute the traffic through anothr ISP. you could also have static routes instead of BGP, but typically in such design , the best approach is to have BGP with the ISPs and IBGP between both routers.
If Static routes in place, then normal tracking route SLA to the ISP and If fails, Secondary default takes place to the next router.
On the LAN , you could have GLBP or Multiple HSRP groups pointing to differnet GWs, so that the hosts inside points to differnt HSRP Active group at a time.
Scenario 2:
If you dont have PUblic IP subnet, then loadbalncing cant be achieved, the only way is to have redundancy and nat configuration on the routers with the same previous setup on the LAN.
Keep in mind , If you have servers inside , this setup is also require additional attention, as you cant have servers using different IP pools connecting to the Internet.
HTH
Mohamed
