How to Configure a router for Dual ISPs

[saashaa747]

The Scenario is :

We have 2 ISPs and a Cisco router 2911  , 

I would like to know how to configure the router that a ISP is primary and another ISP is backup 

while the primary ISP work the secondary must not work (standby), so when the primary ISP link is disconnected

the secondary ISP must connect automatically , 

How to configure the router for above scenario ???

[Mark Malone]

If its just 1 router containing both links try this 2 default routes to each ISP , one of them weighted tracking ISP default route 1 which uses ip sla to confirm link is still valid , when it fails to reach 8.8.8.8 it will be removed from rib and then 2nd backup weighted default will go in

ip route 0.0.0.0 0.0.0.0 x.x.x.x track 1

ip route 0.0.0.0 0.0.0.0 x.x.x.x 225 ----This would be the backup ISP as its weighted

track 1 ip sla 1 reachability

Then track a route upstream like below ip sla

ip sla 1
 path-echo 8.8.8.8 source-ip 1.1.1.1
 frequency 5
ip sla schedule 1 life forever start-time now