GarrettCom Magnum 3000 - Manual (Page 15)

Magnum 3000 Stackable Hubs Installation and User Guide (07/06)
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The IRB ribbon cables supplied with each Magnum 3000 base unit are slightly
longer than the base unit height. Thus, an IRB cable segment has a small arc shape when
it is properly installed. It is possible to have some long IRB ribbon cable segments, up to
a few meters in length, for service loops and such. The operation of the stack will not be
impaired by longer IRB ribbon cables. Stacks with total IRB lengths of as much as ten
meters can be implemented. However, non-standard IRB cable lengths must be specially
made.
The IRB ribbon cables may be installed and/or removed while a Magnum 3000
unit is powered without causing damage to the electronic circuits in that unit or any
others in a Magnum 3000 stack. This is convenient for expanding a stack without
shutting down the network, and for performing diagnostics and service on potentially
faulty units operating in a stack. CAUTION: disconnecting an IRB ribbon cable can
cause operational upsets by breaking the interconnection among the stacked units
previously operating as a single repeater and/or with one SNMP agent.
2.3.2
Segmenting a Magnum 3000 Stack with a Special Segmenting
Cable
Magnum 3000 Stackable Hubs are typically stacked as described in Section
2.3.1. However, it may be desirable to stack the 3000s so that they operate as separate
repeater units. This will normally be done to manage several separate hubs (or small
stacks) with a single 3000 AGT SNMP Agent box. In this situation, single units or
several small stacks of units may be connected using SRC Segmenting Cables (part
numbers SRC-2 and SRC-4, available as a spare part from GCI). Hubs connected via an
IRB Segmenting Cable do not transmit or receive normal Ethernet traffic through the
IRB.
GCI supports this non-standard configuration, making special stacking cable
available (see Models SRC-2 and SRC-4 in the Spare Parts Price List) to provide the
flexibility to break apart managed stacks into multiple collision domains for higher
performance, while still maintaining the advantages of one SNMP agent.
Consider the case where it is desired to divide a managed stack into two
segments and insert a local bridge to increase performance (see Figure 2.3.2a).
Normally, it would be necessary to add another SNMP agent to maintain full
management. However, using the special Segmenting cable option, it is possible to
remove one standard IRB cable and replace it with an SRC cable. This divides the stack