code: def unmap_vc(self, port1, dlci1, port2, dlci2):
          
  
          if port1 not in self._nios:
              raise DynamipsError("Port {} is not allocated".format(port1))
  
          if port2 not in self._nios:
              raise DynamipsError("Port {} is not allocated".format(port2))
  
          nio1 = self._nios[port1]
          nio2 = self._nios[port2]
  
          yield from self._hypervisor.send('frsw delete_vc "{name}" {input_nio} {input_dlci} {output_nio} {output_dlci}'.format(name=self._name,
                                                                                                                                input_nio=nio1,
                                                                                                                                input_dlci=dlci1,
                                                                                                                                output_nio=nio2,
                                                                                                                                output_dlci=dlci2))
  
          log.info('Frame Relay switch "{name}" [{id}]: VC from port {port1} DLCI {dlci1} to port {port2} DLCI {dlci2} deleted'.format(name=self._name,
                                                                                                                                       id=self._id,
                                                                                                                                       port1=port1,
                                                                                                                                       dlci1=dlci1,
                                                                                                                                       port2=port2,
                                                                                                                                       dlci2=dlci2))
          del self._active_mappings[(port1, dlci1)]
docs: Deletes a Virtual Circuit connection (unidirectional).
  
          :param port1: input port
          :param dlci1: input DLCI
          :param port2: output port
          :param dlci2: output DLCI