A controller stack can
have one stacking-capable controller connected through their StackWise-480
ports; which implies that the stack has two members- an active and a standby
controller. The stack member work together as a unified system using the use
the StackWise-480 technology. If the active controller becomes unavailable, the
standby controller assumes the role of the active switch, and continues to the
keep the stack operational.
The active controller
contains the saved and running configuration files for the controller stack.
The configuration files include the system-level settings for the controller
stack and the interface-level settings the stack member. The stack member has a
current copy of all these files for back-up purposes. The controllers in the
stack use Cisco StackWise-480 technology which provides a robust distributed
forwarding architecture through each stack member switch and a unified, fully
centralized control and management plane to simplify operation in a large-scale
network design.
In the stack, all
configuration in the active unit is synced to the standby unit once standby
unit changes its state from member to the hot standby state. Thus, all the
start-up configuration available in the unit prior to synchronization is lost.
If you would need the start-up configuration of the standby unit again, you
must save the startup configuration of the unit in secondary memory- Flash
memory to reuse the configurations later.
You must use the
following Cisco StackWise-480 and Cisco StackPower cables to connect the units
in the stack.
Stack Cable
|
Description
|
STACK-T1-50CM
|
Cisco StackWise-480 50cm stacking cable spare
|
STACK-T1-1M
|
Cisco StackWise-480 1m stacking cable spare
|
STACK-T1-3M
|
Cisco StackWise-480 3m stacking cable spare
|
CAB-SPWR-30CM
|
Cisco Catalyst 3850 StackPower cable 30cm spare
|
CAB-SPWR-150CM
|
Cisco Catalyst 3850 StackPower cable 150cm spare
|
When you reboot the
controller while on stack, you must ensure that you deactivate the already
existing licenses configured on the controllers. This is because while you
perform a reboot, the controller uses the highest activated (EULA accepted)
license level as the reboot license while on stack.
In the stack, all
configuration in the active unit is synced to the standby unit once standby
unit changes its state from member to the hot standby state. Thus, all the
start-up configuration available in the unit prior to synchronization is lost.
If you would need the start-up configuration of the standby unit again, you
must save the startup configuration of the unit in secondary memory- Flash
memory to reuse the configurations later.
When you use the
controller stack, all the six controller ports of both the controllers are
combined hence providing an availability of 12 ports for usage. The bandwidth
of a controller port is a 10 gig ethernet port; however on combination of 12
ports the controller, a throughput of 60 Gbps is only available for use. These
ports can be combined to form an Etherchannel, a flex link, or a Link
Aggregation Group (LAG).
Hello messages are sent and received by all stack members.
-
If a stack member does not respond, that member is removed from the
stack.
-
If the standby controller does not respond, a new standby controller
is elected.
-
If the active controller does not respond, the standby controller
becomes the active controller.
In addition, keepalive messages are sent and received between the active
and standby controllers.
-
If the standby controller does not respond, a new standby controller
is elected.
-
If the active controller does not respond, the standby controller
becomes the active controller.