For a waveguide consisting of multiple layers of dielectric material, a mode eigenfunction of the waveguide can be computed either from the outer-most layer inward or from the inner-most layer outward once the guide wavenumber is known. The guidance condition requires that the eigenfunction of a mode is independent of these two different computation procedures. This requirement can be used for checking the accuracy of numerical computation. When significant discrepancies between these two procedures were observed during a recent revision of a waveguide mode based tropospheric propagation program, it was found that one of the two procedures converged to the mode eigenfunction much faster. This consistency condition has been utilized successfully to relax the requirement on eigenvalue accuracy by identifying the procedure which converges to the correct mode eigenfunction faster.