how to prevent a routing loop an an open interview question

[Astronotus]

As an interview question today, I was given a very crafty, open ended question that I could have obviouslyy answered in one half-dozen different ways, so I think it will be great to see what people have to say?  This is for a Sr. Network Engineer position with design work included. 

How do you avoid a routing loop?

[Philip D'Ath · Accepted solution]

One common approach is to apply a tag to the route, and then make sure you don't redistribute any routes with that tag.