User guide

Managing OmniSwitch 6800 Series Stacks Roles Within the Stack
OmniSwitch 6800 Series Hardware Users Guide June 2007 page 3-7
Using Switch Uptime
A user can override both the MAC address and saved slot methods for determining a stack’s primary
management module. This is done by controlling the uptime of switches in the stack. If all elements of a
stack are powered off, the user can force a particular switch to become primary by powering on that
switch and waiting a minimum of 15 seconds before powering on any other switches. This can be useful if
the user wants a switch placed in a specific location—e.g., the top-most switch in a stack—to become the
primary.
As with the lowest MAC address method, the primary management module is dynamically assigned slot
number 1 when the stack is booted.
For more information on using saved slot information to determine the primary switch in a stack, refer to
the diagram below:
Primary Management Module Selection Using Switch Uptime
Powered On
Powered On
Powered On
Off
Four OmniSwitch 6800 Series switches are stacked and connected via
stacking cables. All switches are currently powered off. The user powers
on a single switch in the stack. In this case, the bottom-most switch is
powered on.
The user now powers on the remaining switches in the stack in short
succession.
In this example, when the remaining switches come online, each has a
lower saved slot value than the switch powered on at step 1. However,
the switch powered on at step 1—with its slot value of 8—retains its
primary management role. The joining switches are essentially ineligible
for primary status because they are considered “late arrivals.”
For the primary switch to forfeit its role to the switch with the lowest
assigned slot number (in this case, slot number 1), the stack must be
rebooted by the user either by issuing the
reload all command or by
powering off and powering on all switches in close succession.
1
2
3
Off
Off
Powered On
Off
Off
Off
Primary
(Saved Slot 8)
Primary
(Saved Slot 8)
Saved Slot 3
Saved Slot 1
Saved Slot 2
Primary
(Saved Slot 8)
The user allows a minimum of 15 seconds to pass. Because no
other switches have joined the stack, the switch that was powered
on considers itself a stand-alone. The switch assumes a primary
role by default—even if there is a high saved slot number in its
boot.slot.cfg file (e.g., 8).
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