Service Manual

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retained during the failover, as is the stack MAC address. 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.
To view failover details, use the show redundancy command.
MAC Addressing on Stacks
The stack has three MAC addresses: the chassis MAC, interface MAC, and null interface MAC.
All interfaces in the stack use the interface MAC address of the management unit, and the chassis MAC
for the stack is the master’s chassis MAC. 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 different unit
becomes the stack manager.
NOTE: If the removed management unit is brought up as a standalone unit or as part of a different
stack, there is a possibility of MAC address collisions.
A standalone is added to a stack. The standalone and the master unit have the same priority, but the
standalone has a lower MAC address, so the standalone reboots. In the second example, a standalone is
added to a stack. The standalone has a higher priority than the stack, so the stack (excluding the new
unit) reloads.
Example of Adding a Standalone with a Lower MAC Address to a Stack
----------STANDALONE BEFORE CONNECTION---------------
Standalone#show system brief
Stack MAC : 00:01:e8:d5:ef:81
-- Stack Info --
Unit UnitType Status ReqTyp CurTyp Version Ports
------------------------------------------------------
0 Management online
S4048-ON S4048-ON
1 Member not present
2 Member not present
3 Member not present
4 Member not present
5 Member not present
6 Member not present
[output omitted]
Standalone#show system | grep priority
Master priority : 0
-----------STACK BEFORE CONNECTION----------------
Stack#show system brief
Stack MAC : 00:01:e8:d5:f9:6f
-- Stack Info --
Unit UnitType Status ReqTyp CurTyp Version Ports
---------------------------------------------------
0 Standby online
S4048-ON
1 Management online S4048-ON
2 Member not present
3 Member not present
4 Member not present
5 Member not present
6 Member not present
940
Stacking