62 CHAPTER 3: P ORT O PERATIONBy default, port loopback detection and the loopback detection control function ontrunk and hybrid ports are disabled. The detection interval is 30 seconds, and thesystem detects the default VLAN on the trunk and hybrid ports.Configuring VCTYou can start the virtual cable test (VCT) to make the system test the cable connectedto the current electrical Ethernet port, and the system will return the test results in fiveseconds. The test items include: whether short or open circuit exists in the Rx/Txdirection of the cable, and what is the length of the cable in normal status or thelength from the port to the fault point of the cable.VCT Configuration ExampleNetwork requirementsStart VCT to make the system test the cable connected to the following port.Configuration procedure1 Enter the system view. system-view2 Enter the Ethernet1/0/1 port view.[S5500] interface Ethernet 1/0/13 Start VCT.[S5500-Ethernet1/0/1] virtual-cable-testCable status: abnormal(open), 7 metresPair Impedance mismatch: yesPair skew: 4294967294 nsPair swap: swapPair polarity: normalInsertion loss: 7 dbReturn loss: 7 dbNear-end crosstalk: 7 dbEthernetPort SecurityFeaturesPort security is a security mechanism to control network access. It is an expansion ofthe current 802.1x and MAC address authentication. This scheme controls theincoming/outgoing packets on port by checking the MAC addresses contained indata frames, and provides multiple security and authentication modes; this greatlyimproves the security and manageability of the system.The port security scheme provides the following features:1 NTK: Need to Know feature. By way of checking the destination MAC addresses ofthe data frames to be sent from a port, this feature ensures that only successfullyTable 46 Configure VCTOperation Command DescriptionEnter system view system-view -Enter Ethernet port view interfaceinterface-typeinterface-number-Start VCT to make the system testthe cable connected to the currentelectrical Ethernet portvirtual-cable-test RequiredBy default, this test is not started.
