59Debugging and DiagnosticsThis chapter describes debugging and diagnostics for the device.Offline DiagnosticsThe offline diagnostics test suite is useful for isolating faults and debugging hardware.The diagnostics tests are grouped into three levels:• Level 0 — Level 0 diagnostics check for the presence of various components and perform essentialpath verifications. In addition, Level 0 diagnostics verify the identification registers of the componentson the board.• Level 1 — A smaller set of diagnostic tests. Level 1 diagnostics perform status/self-test for all thecomponents on the board and test their registers for appropriate values. In addition, Level 1diagnostics perform extensive tests on memory devices (for example, SDRAM, flash, NVRAM,EEPROM) wherever possible.• Level 2 — The full set of diagnostic tests. Level 2 diagnostics are used primarily for on-board loopbacktests and more extensive component diagnostics. Various components on the board are put intoLoopback mode and test packets are transmitted through those components. Level 2 diagnostics alsoperform snake tests using virtual local area network (VLAN) configurations.Important Points to Remember• You can only perform offline diagnostics on an offline standalone unit or offline member unit of astack of three or more. You cannot perform diagnostics on the management or standby unit in a stackof two or more; if you do, a message similar to this displays: Running Diagnostics on master/standby unit is not allowed on stack.• Perform offline diagnostics on one stack member at a time.• Diagnostics only test connectivity, not the entire data path.• Diagnostic results are stored on the flash of the unit on which you performed the diagnostics.• When offline diagnostics are complete, the unit or stack member reboots automatically.Running Offline DiagnosticsTo run offline diagnostics, use the following commands.For more information, refer to the examples following the steps.1. Place the unit in the offline state.EXEC Privilege modeoffline stack-unit stack-unit-numberYou cannot enter this command on a MASTER or Standby stack unit.1036 Debugging and Diagnostics
