Dielectric spectroscopy was applied to investigate the dynamic properties of nematic liquid crystal - 5CB confined in 2000 cylindrical pores of Anopore membranes with the molecules oriented perpendicular to the pore wall with lecithin treated surface. This allows the investigation of the librational (tumbling) mode since the probing electric field is parallel to the pore axis. We found that the dynamics of the librational mode is totally different from the behavior observed in investigations of relaxation due to reorientation of molecules around their short axis. The interpretation of the temperature dependence of relaxation times in nematic phase needs the involvement of the temperature dependence of orientational order parameter. In the supercooled state, the temperature dependence of the librational mode did not follow the behavior observed in the nematic phase and shows a sharp increase while the temperature is decreased that is mainly determined by the variations of viscosity.