Reference 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, traffic 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 traffic 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 traffic on the new master switch is uninterrupted. The
control plane manages the Protocol traffic.
3. A member switch is elected as the new standby. Data traffic on the new standby is uninterrupted.
The control plane prepares for operation in Warm Standby mode.
910
Stacking