Administrator Guide

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.
The following syslog messages are generated when a member unit fails:
Dell#May 31 01:46:17: %STKUNIT3-M:CP %IPC-2-STATUS: target stack unit 4 not responding
May 31 01:46:17: %STKUNIT3-M:CP %CHMGR-2-STACKUNIT_DOWN: Major alarm: Stack unit 4 down - IPC
timeout
Dell#May 31 01:46:17: %STKUNIT3-M:CP %IFMGR-1-DEL_PORT: Removed port: Te 4/1-32,41-48, Fo 4/
49,53
Dell#May 31 01:46:18: %STKUNIT5-S:CP %IFMGR-1-DEL_PORT: Removed port: Te 4/1-32,41-48, Fo 4/
49,53
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 Aggregator 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. Protocol trac is managed by the
control plane.
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 Aggregators 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.
To re-enable a downed stacking port, power cycle the stacked switch on which the port is installed.
The following is an example of the stack-link apping error message.
--------------------------------------MANAGMENT UNIT-----------------------------------------
Error: Stack Port 49 has flapped 5 times within 10 seconds.Shutting down this stack port now.
Error: Please check the stack cable/module and power-cycle the stack.
10:55:20: %STKUNIT1-M:CP %KERN-2-INT: Error: Stack Port 50 has flapped 5 times within 10
seconds.Shutting down this stack port now.
Stacking
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