In this paper, we propose a novel hybrid strategy that combines mixed integer linearprogramming (MILP) formulation with different alternative routing approaches that is capable ofsolving, simultaneously, the routing, modulation format and spectrum assignment problem in thedesign of elastic optical networks. We extend our proposal to a path-link formulation that, althoughit is not guaranteed to find the optimal solution, it has shown reasonable solutions within inferiorsimulation time, allowing it to be used in not very short networks. We also compare our proposalwith another MILP formulation and three adapted heuristics, all available in the literature. Theresults show the benefits of our proposal considering diverse simulation scenarios and differentnumber of modulation formats over19realistic networks in terms of simulation run time andmaximum number of used set of slots.