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APX 8000/MAX TNT/DSLTNT Physical Interface Configuration Guide Preliminary May 9, 2000 2-1
2
Configuring Shelf-Controller Redundancy
(APX 8000)
Overview of redundancy operations
The APX 8000 can operate with a single shelf controller or with two redundant shelf
controllers. When the APX 8000 runs with two shelf controllers, one controller takes on the
active role of primary controller while the other performs as the passive, secondary controller
that automatically takes over control of the system if the primary controller fails. In an APX
8000 with a single shelf controller, no controller redundancy exists.
In an APX 8000 with two shelf controllers, the primary shelf controller performs all controller
operations for the APX 8000:
• Managing the slot cards
• Maintaining a central repository of the unit’s configurations (including the current
NVRAM configuration)
• Performing call control and processing operations
• Managing all centralized functions, such as SNMP access and communication with a
RADIUS server.
In addition, all profiles are modified on the primary controller. When a configuration change is
made on the primary controller, the entire configuration is copied to the secondary controller.
The secondary controller must be loaded with the same boot and operational code as the
primary controller.
Shelf-controller startup and primary election
When an APX 8000 with redundant controllers boots up, each shelf controller passes the
power-on self tests (POST) during the boot code loading process. The controllers establish
communication with each other over the packet bus, and exchange context information
(Redundancy profile and Redundancy-Stats profile information) through the heartbeat
protocol. Each controller has its own context (known as Context[1] or Context[2]), which is
associated with the controller’s serial number. The controllers use the context information to
track each other’s status.
Overview of redundancy operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1
Configuring the APX 8000 for shelf-controller redundancy . . . . . . . . . . . . . . . . . . . . . 2-3
Obtaining status information about redundant shelf controllers . . . . . . . . . . . . . . . . . . 2-9