Alcatel-Lucent 6850-48 Hardware Manual

Managing OmniSwitch 6850 Series Stacks

Roles Within the Stack

OmniSwitch 6850 Series Hardware Users Guide

page 4-7

The saved slot number is the slot number the switch will assume following a reboot. This information is 
stored in a switch’s boot.slot.cfg file; the switch reads its slot number assignment from this file at bootup 
and assumes the specified slot number within the stack.

If switches in a stacked configuration have no preconfigured slot assignments, the slot number for each 
switch is dynamically assigned by the system software. Slot numbers can also be manually assigned by the 
user. For more information on manually assigning slot numbers, refer to 

.

When a stack with preconfigured slot information is booted, it is not the lowest MAC address that deter-
mines the primary management module. Instead, the slot information stored in each switch’s boot.slot.cfg 
is read by the system software and used in determining the primary. The switch with the lowest saved slot 
number becomes the primary management module. 

Note. Although, for ease-of-management purposes, it is recommended that slot numbers are assigned 
beginning with slot number 1, it is not a requirement. In other words, a stack of four switches can have 
slot assignments 3, 4, 5, and 6. However, it is important that each element in a stack is assigned a unique 
slot number. Do not assign duplicate slot numbers to elements in a stack. Otherwise, one or more switches 
will be forced into pass-through mode. For more information on pass-through mode, refer to 

.

For more information on using saved slot information to determine the primary switch in a stack, refer to 
the diagram below:

Four OmniSwitch 6850 Series switches are stacked; all switches 
are connected via stacking cables. The user configures each 
switch to have a unique saved slot number. When each saved 
slot number is configured, the information is automatically 
written to the boot.slot.cfg file located in the /flash directory of 
each switch. 

The user reloads all the elements in the stack either by 
issuing the reload all command or by physically powering 
off and then powering on all switches.

Instead of assigning the primary management module 
based on the lowest MAC address, the system software 
reads the slot information from each switch’s 
boot.slot.cfg file during the boot process. The switches 
in the stack come up using their assigned slot numbers.

The switch with the lowest assigned slot number automatically 
assumes the primary management role. In this case, the switch 
assigned slot 3 has the lowest slot number in the stack and 
becomes the primary management module.