z external: Performs external loop test. In the external loop test, self-loop headers must be used onthe port of the switch ( for 100M port, the self-loop headers are made from four cores of the 8-corecables, for 1000M port, the self-loop header are made from eight cores of the 8-core cables, thenthe packets forwarded by the port will be received by itself.). The external loop test can locate thehardware 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 RequiredConfiguring the Interval to Perform Statistical Analysis on Port TrafficBy performing the following configuration, you can set the interval to perform statistical analysis on thetraffic of a port.When you use the display interface interface-type interface-number command to display theinformation of a port, the system performs statistical analysis on the traffic flow passing through the portduring the specified interval and displays the average rates in the interval. For example, if you set thisinterval to 100 seconds, the displayed information is as follows:Last 100 seconds input: 0 packets/sec 0 bytes/secLast 100 seconds output: 0 packets/sec 0 bytes/secFollow these steps to set the interval to perform statistical analysis on port traffic:To do... Use the command... RemarksEnter system view system-view —12-8
