Filter OSPF routes redistributed by BGP

Question

I am redistributing OSPF routes inside a network, through BGP. However I don't want to redistribute all the advertised routes from OSPF (specificaly the private networks) to the outside of the AS. How can I prevent some routes from being redistributed in BGP, using route-maps/access-lists?

Answer 1

Create a prefix list for the routes you don't want to allow. Then create a route-map and deny that prefix list, but permit everything else. Use that route-map to filter the routes redistributed into BGP.