Stacking | 973
• MAC address (in case of priority tie): The unit with the higher MAC value becomes the master unit.
The stack takes the MAC address of the master unit and retains it unless it is reloaded.
To view which switch is the stack master, enter the
show system command. Figure 47-1 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.
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 or
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.
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. For
more details, see sections “Add Units to an Existing S-Series Stack on page 985” and “Remove a Unit
from an S-Series Stack on page 995”.
It is possible to reset individual units to force them to give up the
management role or reload the whole stack from the CLI to ensure a fully synchronized bootup.
Figure 47-1. Displaying the Stack Master
FTOS#show system brief
Stack MAC : 00:01:e8:8c:53:32
Reload Type : normal-reload [Next boot : normal-reload]
-- Stack Info --
Unit UnitType Status ReqTyp CurTyp Version Ports
----------------------------------------------------------------------------
0 Member not present
1 Management online S4810 S4810 4810-8-3-12-1447 64
2 Standby online S4810 S4810 4810-8-3-12-1447 64
3 Member online S4810 S4810 4810-8-3-12-1447 64
4 Member online S4810 S4810 4810-8-3-12-1447 64
5 Member not present
6 Member not present
7 Member not present
8 Member not present
9 Member not present
10 Member not present
Virtual IP
The stack can be managed using a single IP, known as a virtual IP, that is retained in the stack even after a
failover. The virtual IP address is used to log in to the current master unit of the stack. Both IPv4 and IPv6
addresses are supported as virtual IPs.
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