13Step Command Remarks5. Enter Ethernetinterface view or portgroup view.• Enter Ethernet interface view:interface interface-typeinterface-number• Enter port group view:port-group manualport-group-nameUse either command.To configure loopback detection on oneinterface, enter Ethernet interface view.To configure loopback detection on a groupof Ethernet interfaces, enter port group view.6. Enable loopbackdetection on theinterface.loopback-detection enable Disabled by default.7. Enable loopbackdetection control on atrunk port or a hybridport.loopback-detection controlenableOptional.Disabled by default.8. Enable loopbackdetection in all theVLANs on the trunk orhybrid port.loopback-detection per-vlanenableOptional.By default, a trunk or hybrid port performsloopback detection only in its port VLAN ID(PVID).9. Set the protectiveaction to take on theinterface when a loopis detected.loopback-detection action{ no-learning | semi-block |shutdown }Optional.By default, a looped interface drops theincoming packets and correctly sendspackets the system generates traps and logmessages, and deletes all MAC addressentries of the looped interface.With the shutdown keyword specified, theswitch shuts down the looped ports and settheir physical state to Loop down. When alooped port recovers, you must use the undoshutdown command to restore its forwardingcapability.Setting the MDI mode of an Ethernet interfaceIMPORTANT:Fiber ports do not support the MDI mode setting.You can use both crossover and straight-through Ethernet cables to connect copper Ethernet interfaces.To accommodate these types of cables, a copper Ethernet interface can operate in one of the followingMedium Dependent Interface (MDI) modes:• Across mode• Normal mode• Auto modeA copper Ethernet interface uses an RJ-45 connector, which comprises eight pins, each of which plays adedicated role. For example, pins 1 and 2 transmit signals, and pins 3 and 6 receive signals. The pinrole varies by the MDI modes as follows:• In normal mode, pins 1 and 2 are transmit pins, and pins 3 and 6 are receive pins.• In across mode, pins 1 and 2 are receive pins, and pins 3 and 6 are transmit pins.
