def dpid_to_mac (dpid):
        """Generate hex MAC address from a given int ID.
        Args:
            dpid (int): Integer ID of a switch, e.g. 1,2,3, and so on.

        Returns:
            str: MAC address without any colon or comma sign (only hex numbers).

        """

        return "%012x" % (dpid & 0xffFFffFFffFF,)