1-6Enabling Loopback TestYou can configure the Ethernet port to run loopback test to check if it operates normally. The portrunning loopback test cannot forward data packets normally. The loopback test terminatesautomatically after a specific period.Follow these steps to enable loopback test:To do... Use the command... RemarksEnter system view system-view —Enter Ethernet port view interface interface-type interface-number —Enable loopback test loopback { external | internal } Requiredz external: Performs external loop test. In the external loop test, self-loop headers must be used onthe port of the switch ( for 1000M port, the self-loop header are made from eight cores of the 8-corecables, then the packets forwarded by the port will be received by itself.). The external loop test canlocate the hardware failures on the port.z internal: Performs internal loop test. In the internal loop test, self loop is established in theswitching chip to locate the chip failure which is related to the port.Note that:z After you use the shutdown command on a port, the port cannot run loopback test.z You cannot use the speed, duplex, mdi and shutdown commands on the ports running loopbacktest.z Some ports do not support loopback test, and corresponding prompts will be given when youperform loopback test on them.Enabling the System to Test Connected CableYou can enable the system to test the cable connected to a specific port. The test result will be returnedin five seconds. The system can test these attributes of the cable: Receive and transmit directions (RXand TX), short circuit/open circuit or not, the length of the faulty cable.Follow these steps to enable the system to test connected cables:To do... Use the command... RemarksEnter system view system-view —Enter Ethernet port view interface interface-typeinterface-number —Enable the system to testconnected cables virtual-cable-test Required
