Thank you for your immediate response.

I am not using the dipole sources, I am using mode sources, and I wanted to excite two mode sources at a time with two different frequencies placed a diferent distances inside the waveguide. For this, I am really looking for a higher order mode of HE\EH of index100.

But in this case, I am using 36 um diameter of a cylindrical waveguide and I am searching for round 2000 modes (have used your suggestion here using advanced options) between the index 1.1 to 1. I would rather see only HE-69 mode at 1.002139 index (Please find the attached picture), do I really get HE-100 in this case? Please suggest.

Symmetry BC's are working fine for me, thanks for this. But as I am looking for two consecutive sources, even and odd, if I use symmetry BC's the FDE solver is showing only one mode (either even or odd), so it is critical for me. Do you get this point?