Hello Expert,
When I tested ISP Redundancy, I found that it is not compatible with PBR.
Here is structure.

So I changed to use two next hops on the static route, and use priority to divide the primary and the secondary.

I found out that the only way to checkpoint to make sure the route works is to make sure the next hop is viable.
For example, if I turn off Gi0/0 on S3 it switches to the second line for service, but if I turn off Gi0/1 on S3 the checkpoint continues to the first line without switching.
Is there a way to configure the first line to ping the IP of the external network? (transparent monitor)
For example, ping 8.8.8.8 through 30.30.30.30 to make sure that this line can reach the external network.
Thanks