User Manual

Troubleshooting a Switch Stack
To perform troubleshooting operations on a switch stack, use the following commands on the master
switch.
1. Displays the status of stacked ports on stack units.
show system stack-ports
2. Displays the master standby unit status, failover configuration, and result of the last master-standby
synchronization; allows you to verify the readiness for a stack failover.
show redundancy
3. Displays input and output flow statistics on a stacked port.
show hardware stack-unit unit-number stack-port port-number
4. Clears statistics on the specified stack unit. The valid stack-unit numbers are from 0 to 5.
clear hardware stack-unit unit-number counters
5. Displays the current operational mode of the Aggregator (standalone or stacking) and the mode in
which the Aggregator will operate at the next reload.
show system stack-unit unit-number iom-mode
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.
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 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.
194
Stacking