Cisco 500 Series Administration Manual page 97

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• Change the stack mode of a device to one of the stacking modes, change
the unit ID, stack ports, and the speed of the stack ports of all the devices in
a stack.
• Change the system mode (Layer 2/3) of a standalone device or of the stack.
• Change the queues mode from 4 to 8 supported queues or vice versa.
Information about these modes is stored in the configuration file, as follows:
• Configuration File Header—Contains the system mode and the queues
mode (even if these are the default values).
• Configuration File Body—Contains configuration commands.
Backwards Compatibility
The following modes have been expanded in the current software version of the
device. Care must be taken when using these features in previous software
versions:
• Stack Port LAG—If a unit whose software supports stack ports in LAGs is
connected to a unit whose software does not support stack ports in LAGs,
the stack port connecting the units is not made a member of the stack LAG.
The units are connected through the stack ports, and the stack master
copies its software to the other unit. The software copied depends on the
unit which becomes the master.
• Queues Mode—This mode can be changed from 4 QoS queues to 8 QoS
queues. There is no issue when upgrading from previous software versions
that did not support 8 queues, since the 4-queue mode is the default
queues mode in the current software version. However, when changing the
queues mode to 8 queues, the configuration must be examined and
adjusted to meet the desired QoS objectives with the new queues mode.
Changing the queues mode takes effect after rebooting the system. Queue-
related configuration that conflicts with the new queues mode is rejected.
• Stacking Mode—The Stacking mode has been expanded to include hybrid
stacking modes. There is no problem in upgrading from previous software
versions, since the device will boot with the existing stacking mode (Native
Stacking mode). If you want to downgrade software from a device that was
configured in a hybrid stacking mode to a software version that does not
support hybrid stacking, configure the device to Native Stacking mode first.
Administration: Stack Management
Cisco 500 Series Stackable Managed Switch Administration Guide
System Modes