Users Guide

• Switch failure
• Inter-switch stacking link failure
• Switch insertion
• Switch removal
If the master switch goes off line, the standby replaces it as the new master.
NOTE: For the Aggregator, the entire stack has only one management IP address.
Stack Master Election
The stack elects a master and standby unit at bootup time based on MAC address. The unit with the
higher MAC value becomes master.
To view which switch is the stack master, enter the show system command. The following example
shows sample output from an established stack.
A change in the stack master occurs when:
• You power down the stack master or bring the master switch offline.
• A failover of the master switch occurs.
• You disconnect the master switch from the stack.
NOTE: When a stack reloads and all the units come up at the same time; for example, when all units
boot up from flash, all units participate in the election and the master and standby are chosen based
on the priority on the MAC address. When the units do not boot up at the same time, such as when
some units are powered down just after reloading and powered up later to join the stack, they do
not participate in the election process, even though the units that boot up late may have a higher
priority configured. This happens because the master and standby have already been elected, hence
the unit that boots up late joins only as a member. Also, when an up and running standalone unit or
stack is merged with another stack, based on election, the losing stack reloads and the master unit
of the winning stack becomes the master of the merged stack. To ensure a fully synchronised
bootup, it is possible to reset individual units to force them to give up the management role; or
reload the whole stack from the command line interface (CLI).
Example of Viewing Stack Members
Dell# show system brief
Stack MAC : 00:1e:c9:f1:00:9b
-- Stack Info --
Unit UnitType Status ReqTyp CurTyp Version Ports
--------------------------------------------------------------------------------
----
0 Management online I/O-Aggregator I/O-Aggregator 8-3-17-46 56
1 Standby online I/O-Aggregator I/O-Aggregator 8-3-17-46 56
2 Member not present
3 Member not present
4 Member not present
5 Member not present
Dell#
Failover Roles
If the stack master fails (for example, powered off), it is removed from the stack topology. The standby
unit detects the loss of peering communication and takes ownership of the stack management, switching
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Stacking