Users Guide

• Switch removal
If the master switch goes o 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 oine.
• 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 ash,
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 congured. 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 o), it is removed from the stack topology. The standby unit detects the loss of
peering communication and takes ownership of the stack management, switching from standby to master. The lack of a standby unit
triggers an election within the remaining units for a standby role.
After the former master switch recovers, despite having a higher priority or MAC address, it does not recover its master role but
instead takes the next available role.
MAC Addressing
All port interfaces in the stack use the MAC address of the management interface on the master switch. The MAC address of the
chassis in which the master Aggregator is installed is used as the stack MAC address.
The stack continues to use the master’s chassis MAC address even after a failover. The MAC address is not refreshed until the stack
is reloaded and a dierent unit becomes the stack master.
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Stacking