4Follow these steps to enable flow control on an interface:To do… Use the command… RemarksEnter system view system-view —Enter Ethernet interface view interface interface-typeinterface-number —Enable flow control flow-controlRequiredBy default, receive flow control isdisabled on an interface.Configuring link down suppression on an Ethernet interfaceThe physical link state of an Ethernet interface is either up or down. Each time the physical link of a portgoes up or comes down, the physical layer reports the change to the upper layers, and the upper layershandle the change, resulting in increased overhead.To prevent physical link flapping from affecting system performance, configure link down suppression todelay the reporting of link down events. The physical layer reports the link down events only when thedelay expires.Follow these steps to configure link down suppression on an Ethernet interface:To do… Use the command… RemarksEnter system view system-view —Enter Ethernet interface view interface interface-typeinterface-number —Set a link down suppressioninterval link-delay delay-timeRequiredLink down suppression is disabledby default.Configuring loopback testing on an Ethernet interfaceYou can perform loopback testing on an Ethernet interface to check whether the interface functionsproperly. Note that the Ethernet interface cannot forward data packets during the testing. Loopbacktesting falls into the following two categories:• Internal loopback testing, which tests all on-chip functions related to Ethernet interfaces. As shownin Figure 2, internal loopback testing is performed on Port 1. During the internal loopback testing,the port sends out a certain number of test packets, which are looped back to the port over theself-loop created on the switching chip.
