3Com 2928 User Guide - Page 108

After selecting a testing type, you need to select a port on which you want to perform the loopback test from the chassis front panel. After that, click Test to start the loopback test, and you can see the test result in the Result text box, as shown in Figure 1-2. Figure 1-2 Loopback test result Configuration Guidelines Note the following when performing a loopback test: z You can perform an internal loopback test but not an external loopback test on a port that is physically down, while you can perform neither test on a port that is manually shut down. z The system does not allow Rate, Duplex, Cable Type and Port Status configuration on a port under a loopback test. z An Ethernet port works in full duplex mode when the loopback test is performed, and restores its original duplex mode after the loopback test. 1-2