Methods and systems of traffic routing in a circuit switched communication network having a plurality of switches and a plurality of trunk groups connecting the switches are disclosed. The methods include a step of determining a set of alternate routing paths for each of a plurality of ordered pairs of the switches, wherein the number of alternate routing paths through each of the trunk groups is constrained to be less than a corresponding first predetermined threshold. In one embodiment, the alternate routing paths are determined by computing a solution to a predetermined integer programming problem. In another embodiment, a heuristic technique is used to determine the alternate routing paths.