Abstract: A network device includes a route selection module configured to select an alternate next hop to use in forwarding network traffic to a destination in the event a primary next hop becomes unavailable, wherein a path to the destination device associated with the alternate next hop does not send packets through the network device. The route selection module computes optimal distances from neighboring devices to the network device, wherein a number of Shortest Path First (SPF) computations required for computing the optimal distances is independent of the number of neighboring devices in the network, identifies as candidate alternate next hops those neighboring devices having distances to the destination that are less than the sum of the optimal distance from the neighboring device to the network device and the optimal distance from the network device to the destination, and selects the alternate next hop from among the stored candidates.

Abstract: In general, the invention is directed to techniques for improving the performance of route filtering methods. More specifically, an interval tree data structure is assembled from one or more address prefix outbound route filter (ORF) entries by partitioning, according to the characteristics of the ORF entries, a two-dimensional space defined by the address prefix and prefix length domains into non-overlapping intervals. Each node in the interval tree represents a non-overlapping interval in the address prefix dimension. In addition, each node includes a distinct tree structure having nodes that maintain information about the ORF entries that map onto the represented interval for various non-overlapping intervals in the prefix length domain. By traversing the two tiers of trees, a network device can quickly determine the appropriate action to apply to a route.