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AT-8000GS Series Gigabit Ethernet Switch Installation Guide
37
automatically switches to a Stacking Failover topology without any system
downtime. An SNMP message is automatically generated, but no stack
management action is required. However, the stacking link or stacking
member must be repaired to ensure the stacking integrity.
After the stacking issues are resolved, the device can be reconnected to
the stack without interruption, and the Ring topology is restored.
Stacking Chain
Topology
In a chain topology, there are two units that have only one neighbor. Every
unit has an uplink neighbor and a downlink neighbor. The chain topology is
less robust than the ring topology. A failure in the chain results in a
topology change to the stack. The location of the failure determines the
severity of this topology change. The chain topology also acts as a fail-
safe for the ring topology. When the ring topology fails, the stack
automatically reverts to the chain topology.
Stacking
Members and
Unit ID
Stacking Unit IDs are essential to the stacking configuration. The stacking
operation is determined during the boot process. The Operation Mode is
determined by the Unit ID selected during the initialization process. For
example, if the user selected stand-alone mode, the device boots as a
stand-alone device.
The device units are shipped with the default Unit ID of the stand-alone
unit. If the device is operating as a stand-alone unit, all stacking LEDs are
off. Once the user selects a different Unit ID, the default Unit ID is not
erased, and remains valid, even if the unit is reset.
Unit ID 1 and Unit ID 2 are reserved for Master-enabled units. Unit IDs 3 to
6 can be defined for stack members.
When the Stacking Master unit boots, or when inserting or removing a
stack member, the Stacking Master initiates a stacking discovering
process.
If two members are discovered with the same Unit ID, the stack continues
to function, however only the unit with the older join time joins the stack. A
message is sent to the user, notifying that a unit failed to join the stack.
For first time Unit ID assignment, see the Installation Guide.
Removing and
Replacing
Stacking
Members
Stacking member 1 and stacking member 2 are Master-enabled units. Unit
1 and Unit 2 are either designated as Stacking Master or Secondary
Master. The Stacking Master assignment is performed during the
configuration process. One Master-enabled stack member is elected
Stacking Master, and the other Master-enabled stack member is elected
Secondary Master, according to the following decision process:
If only one Master-enabled unit is present, it is elected Stacking Master.
If two Master-enabled stacking members are present, and one has been