Tauer:
The condition you describe is independent of the routing protocol being used.
After a routing protocol has converged, it will have determined the best path to a destination network and forward the traffic out a certain interface.
The best way to avoid a single point of failure is to design a network with redundant, equal-cost paths and redundant equipment. When a circuit is failing miserably, you can manually shut down the interface and allow the traffic to take the alternate path.
That having been said, there are automated mechanisms in existence to mitigate the effects of a flapping interface. You can use IP Event Dampening.
IP Event Dampening is a health-check mechanism that you can confgiure on the router to monitor the "flapping" events of an interface. Basically, when the event threshold surpasses a pre-determined number, the interface is effectively shut down, its neighbor relationship with the peer router is removed and all routes learned through the dampened interface are not used.
This helps improve network stability and convergence times and reduces the load on your router's CPU because it doesnt have to cconstantly re-establish neighbor relationships and re-converge everytime the interface flaps.
When the circuit is back online and error free enough to NOT bring the neighbor relationship down, the interface will be restored.
Lastly, if your circuit is running errors, you should aggressively pursue it with your TELCO and demand that they fix it. It's as simple as that. That is the TRUE fix.
You can configure an IP SLA monitor to track thehealth of the device sitting on the other end of the circuit and create conditions under which the router should use an alternate path, but this is typically used with static routing.
http://www.cisco.com/en/US/docs/ios/iproute/configuration/guide/irp_ip_event_damp.pdf
HTH
Victor
