Stack Cabling - Alcatel OS6855-24 Hardware User's Manual

Managing OmniSwitch 6855 Series Stacks

Stack Cabling

Switches in a stack are connected to each other with either copper or fiber stacking cables that are avail-
able in various lengths. Fiber can be used with an SFP+ transceiver.
Stacking cables for OmniSwitches can be connected in any pattern. In other words, the cable connected to
stacking port A of one switch can be connected to either stacking port A or stacking port B of the adjacent
switch. However, it is strongly recommended that the cabling pattern remains consistent across the stack.
In addition, for a stack to have effective redundancy, a redundant stacking cable must be installed between
the upper-most and bottom-most switch at all times. This provides effective failover in the event of a sta
cking link or module failure within the stack.
The diagram below shows two recommended stacking cable patterns. Refer to
page 2-42 for cable specifications.
Note. When planning the stack cabling configuration, keep in mind that the switch connected to stacking
port A of the primary switch will be assigned the secondary management role by default. The diagram
below is for example purposes only, currently only four OS6855-U24X switches can be stacked at a time.
Examples of Stacking Cable Patterns (Chassis Rear Panels Shown)
OmniSwitch 6855 Series Hardware Users Guide
A B
A stack of switches in a crossed (stacking port A to
stacking port B) configuration. Note that a redundant
stacking cable connection exists between the top and
bottom switches. This connection is required for
effective redundancy across the stack.
A B
A stack of switches in a straight (stacking port A to
stacking port A; stacking port B to stacking port B)
configuration. Note that a redundant stacking cable
connection exists between the top and bottom
switches. Again, this connection is required for
effective redundancy across the stack.
September 2011
Stack Cabling
"Stacking Cables" on
page 7-17