Stack Master Election; Failover Roles - Dell PowerEdge M IO Aggregator Command Reference Manual

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, use the
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.
When a stack reloads and all the units come up at the same time; for example, when all units boot up
Note:
from flash, all units participate in the election and the master and standby are chosen based on the MAC
address. When the units do not boot up at the same time; for example, 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; therefore, 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).
Figure 17-16. Displaying the Stack Master
FTOS# show system brief
Stack MAC : 00:1e:c9:f1:00:9b
-- Stack Info --
Unit UnitType Status
------------------------------------------------------------------------------------
0 Management online
1 Standby online
2 Member not present
3 Member not present
4 Member not present
5 Member not present
FTOS#

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 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 take the next available role.
command.
show system
ReqTyp CurTyp
I/O-Aggregator I/O-Aggregator
I/O-Aggregator I/O-Aggregator
Figure 17-16 shows sample
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