White Papers

Failure Scenarios
The following sections describe some of the common fault conditions that can happen in a switch stack and how they are resolved.
Stack Member Fails
Problem: A unit that is not the stack master fails in an operational stack.
Resolution: If a stack member fails in a daisy chain topology, a split stack occurs. If a member unit fails in a ring topology, trac is re-routed
over existing stack links.
Dell#Feb 13 15:26:18: %STKUNIT4-M:CP %IPC-2-STATUS: target stack unit 2 not responding
Feb 13 15:26:19: %STKUNIT4-M:CP %CHMGR-2-STACKUNIT_DOWN: Major alarm: Stack unit 2 down - IPC
timeout
Feb 13 15:26:19: %STKUNIT4-M:CP %IFMGR-5-OSTATE_DN: Changed interface state to down: Te 2/1
Feb 13 15:26:19: %STKUNIT4-M:CP %IFMGR-5-OSTATE_DN: Changed interface state to down: Po 1
Feb 13 15:26:19: %STKUNIT4-M:CP %IFMGR-1-DEL_PORT: Removed port: Te 2/0-11,20-23, Fo 2/
48,52,56,60,
Feb 13 15:26:19: %STKUNIT3-S:CP %IFMGR-1-DEL_PORT: Removed port: Te 2/0-11,20-23, Fo 2/
48,52,56,60,
Unplugged Stacking Cable
Problem: A stacking cable is unplugged from a member switch. The stack loses half of its bandwidth from the disconnected switch.
Resolution: Intra-stack trac is re-routed on another link using the redundant stacking port on the switch. A recalculation of control plane
and data plane connections is performed.
Master Switch Fails
Problem: The master switch fails due to a hardware fault, software crash, or power loss.
Resolution: A failover procedure begins:
1 Keep-alive messages from the master switch time-out after 60 seconds and the switch is removed from the stack.
2 The standby switch takes the master role. Data trac on the new master switch is uninterrupted. The control plane manages the
Protocol trac.
3 A member switch is elected as the new standby. Data trac on the new standby is uninterrupted. The control plane prepares for
operation in Warm Standby mode.
Stack-Link Flapping Error
Problem/Resolution: Stacked switches monitor their own stack ports and disable any stack port that aps ve times within 10 seconds. If
the stacking ports that ap are on the master or standby, KERN-2-INT error messages note the units.
Stacking
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