 What is shielded Cat6? Cat6 comes in various different constructions. There is an external option and also an external steel armoured covered version. For internal Cat6 cables there is unshielded twisted pair, UTP, and shielded twisted pair Cat6, STP, cable. The shielded version is the same in many ways as its counterpart, but with the addition of a foil shielded around the cause of the cables underneath the outer sheath. This adds a layer of protection from external noise and EMI.