1. A computer-implemented method for determining failure recovery information, given a source node, a destination node, and a shared risk group failure on a next hop from the source node to the destination node, the computer-implemented method comprising: a) accepting a graph representing network topology information including the source node and the destination node; b) determining a node which is able to reach the destination node using a route which does not include the source node, wherein a path from the source node to the determined node is not affected by the shared risk group failure; c) storing, in association with the shared risk group failure, both (1) a network address associated with the determined node and (2) an alternative output port of the source node using the shortest path from the source node to the determined node.