Sometimes it is necessary to track an interface state to bring down a certain route.
In my case I have a Multihomed scenario, and two routers. In this case the upstream routers do not know about each other, the downstream routers make the routing decisions for the network.
I have a static route configured pointed to the ISP, I am redistributing that static route to my clients through OSPF. If the state goes down on the interface then the router will take it out of its routing table. You can do this by pining an IP address, UDP Jitter, State, etc.. many ways.
track 100 interface GigabitEthernet0/2 line-protocol
ip route 0.0.0.0 0.0.0.0 184.108.40.206 track 100
You can use commands like:
show track int
show track bri