1. A method, comprising: determining, at a network device, a set of routes to one or more reachable addresses in a computer network; determining a set of no-routes to one or more non-reachable addresses in the computer network; aggregating the routes and no-routes into one or more reachable route prefixes within which being one or more corresponding non-reachable no-route prefix exceptions; and utilizing the route prefixes and no-route prefix exceptions.