def modifyPortMediaType(self, portList='all', mediaType='fiber'):
        """
        Description
           Modify the port media type: fiber, copper, SGMII

        Parameters
           portList: <'all'|list of ports>: 
                     <list>: Format: [[ixChassisIp, str(cardNumber1), str(portNumber1])]...]
                     Or if portList ='all', will modify all assigned ports to the specified mediaType.

           mediaType: <str>: copper, fiber or SGMII
        """
        self.ixnObj.logInfo('modifyPortMediaType: {0}'.format(mediaType))
        response = self.ixnObj.get(self.ixnObj.sessionUrl+'/vport')
        if portList == 'all':
            #vportList = self.getAllVportList()
            portList = self.getPhysicalPortsFromCreatedVports()

        # vportList: ['/api/v1/sessions/1/ixnetwork/vport/1', '/api/v1/sessions/1/ixnetwork/vport/2']
        vportList = self.getVportFromPortList(portList)
        for vport in vportList:
            response = self.ixnObj.get(self.ixnObj.httpHeader+vport, silentMode=True)
            portType = response.json()['type']
            self.ixnObj.patch(self.ixnObj.httpHeader+vport+'/l1Config/'+portType, data={'media': mediaType})