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SmartStack STS-8SU & STS-SM Installation and User Guide Switch Stacker Theory of Operation
Creating a Switch Stack
You can create a stack of up to eight switches using the SmartStack STS-8SU
Stacker Unit. The following sections describe how this stack is formed.
SmartStack STS-8SU Stacker Unit Description
The STS-8SU Stacker unit is an eight-port switch matrix interface, that can connect
up to eight SmartStack Token Ring switches. Each SmartStack Token Ring switch
will discover whether it is connected to a switch stacker unit and whether there are
other SmartStack Token Ring switches connected to the switch stacker. The
connected switches and the switch stacker unit will combine logically to form a
stack.
The stacker itself, as well as any of the stacked switches, can be either on or off
when you connect or disconnect a switch in the stack. A proprietary shielded cable,
one meter in length, with 50-pin SCSI-2 type connectors is used to connect the
stacker equipment. The cable has
crossover
wiring—either end can connect to the
switch stacker or to the SmartStack Token Ring switches. The cable is plugged
directly into a stack port I/O connector on the back of the STS-8SU External
Stacker Unit. The other end is plugged into the SmartStack STS-LM Link Module
interface card that is installed in the expansion slot on the back panel of the switch.
For a description of the features and physical specifications of the STS-8SU
External Stacker Unit, see Chapter 1, “Overview and Specifications”. For details
on the installation of the STS-8SU External Stacker Unit, see Chapter 4,
“Installation”.
Forming a Multi-Unit Switch Stack
When you turn on the switches, they run a set of self-diagnostics. After the
diagnostics, the switches run a stack discovery mode. During this mode, if two or
more switches are connected to a SmartStack STS-8SU Stacker Unit, the switches
will sense the connection and combine logically to create a stack configuration.
As soon as stack discovery mode has finished, two things happen:
1. Each switch is assigned a
box number
.
The box number is determined by the port number on the switch stacker. For
example, the switch that is plugged into port 3 on the SmartStack STS-8SU
Stacker Unit receives the box number 3. The box number remains the same for
the switch as long as it is plugged into the same port. If a switch is connected to
another port, the box number for that switch will change to correspond to the
new port number.