The show interfaces serial 0 command further proves that there is some problem at the interface level. Too many drops are occurring at the interface level. This is the cause of the route flapping. In the case of Frame Relay, the Frame Relay broadcast queue must be tuned. Tuning the Frame Relay broadcast queue is out of the scope of this book; several papers at Cisco's Web site discuss how to tune the Frame Relay broadcast queue.
In a non-Frame Relay situation, the input or output hold queue might need to be increased. Example 3-130 shows that after fixing the interface drop problem, route flapping disappears.
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