User's Manual

89
Configuring a loopback test
You can check whether an Ethernet port operates correctly by performing Ethernet port loopback test.
During the test time, the port cannot forward data packets correctly.
Ethernet port loopback test has the following types:
• Internal loopback test—Establishes self loop in the switching chip and checks whether there is a
chip failure related to the functions of the port.
• External loopback test—Uses a loopback plug on the port. Packets forwarded by the port will be
received by itself through the loopback plug. The external loopback test can be used to check
whether there is a hardware failure on the port.
Configuration guidelines
When you configure a loopback test, follow these restrictions and guidelines:
• When a port is physically down, you cannot perform an external loopback test on the port.
• After a port is shut down manually, you can perform neither internal nor external test on the port.
• When a port is under loopback test, you cannot apply Rate, Duplex, Cable Type, and Port Status
configuration to the port.
• An Ethernet port operates in full duplex mode when a loopback test is performed. It restores its
original duplex mode after the loopback test is finished.
Configuration procedure
1. From the navigation tree, select Device > Loopback.
Figure 75 Loopback test page
2. Select External or Internal for loopback test type.
3. Select an Ethernet interface from the chassis front panel.