74 Chapter 2 System Diagnostics and StatisticsStep Action1 Remove the unit you want to test from the stack.2 Disconnect the stacking cables and any active cables connectedto the ports on the unit.3 Go to NNCLI via serial interface.4 Enable action mode.enable5 Run the internal loopback test.stack loopback-test internal6 Check the results of the command. The "stack loopback-test internaloutput" (page 74) table shows the output from a pass and from afailure.stack loopback-test internal outputPass FailTesting uplink port … okTesting downlink port … okInternal loopback test PASSEDTesting uplink port … FailedTesting downlink port … okInternal loopback test FAILED—End—Testing the stack cablesVerify the integrity of the stack cables using the external loopback test.Prerequisites for testing stack cables• The internal loopback test passed. See "Testing the stack ports" (page73).• Any previous tests have finished running.Step Action1 Remove the suspect unit from the stack.2 Power up the suspect unit.3 Connect a stacking cable from the stack uplink port to the stackdownlink port.Nortel Ethernet Routing Switch 5500 SeriesConfiguration - System MonitoringNN47200-505 03.01 Standard5.1 27 August 2007Copyright © 2005 - 2007, Nortel Networks.
