Cisco Systems 78-16019-02 manual Redundant Operation Requirements

Chapter 3 Initial Configuration

About CPU Switch Module Redundancy

Table 3-2 CPU Switch Module Software States

State	Description
Disabled	The standby CPU switch module is not yet running the system image or is in
	maintenance mode.
Standby cold	The standby CPU switch module is running the system image but has not
	begun to synchronize data from the active CPU switch module.
Standby hot	The standby CPU switch module has fully synchronized the configuration and
	other data from the active CPU switch module. It will remain in the
	hot-standby state until a switchover occurs.
Active	The CPU switch module is in the active hardware state and has completed all
	switchover or initial bootup processing. It is fully ready to control the system.

Redundant Operation Requirements

For fully redundant operation, the following requirements must be met:

•Two CPU switch modules are required.

•The CPU switch modules must have identical hardware configurations. This includes variables such as DRAM size, and so on.

•Both CPU switch modules must have the same functional image.

•Both CPU switch modules must be running compatible system images. System images are compatible across one major release.

•Both the running and startup configurations are automatically synchronized between the CPU switch modules.

•Both CPU switch modules must be set to autoboot (a default setting).

If these requirements are met, the Cisco ONS 15530 runs in redundant mode by default. If they are not met, the system is conditionally redundant.

Note For detailed information on updating system images, see the “Updating System Images on Redundant Processors” section on page 13-14 .

Conditions Causing a Switchover from the Active CPU Switch Module

The following conditions can cause a switchover from the active CPU switch module to the standby CPU switch module:

•The active CPU switch module is removed or swapped. When the CPU switch module functioning as the active CPU switch module is removed, the standby CPU switch module takes over. The Cisco ONS 15530 is nonredundant until a second CPU switch module is inserted.

•The active CPU switch module is rebooted. When a CPU switch module functioning as the active CPU switch module is rebooted, it relinquishes its active role if the standby CPU switch module has reached the hot-standby state.

	Cisco ONS 15530 Configuration Guide and Command Reference
3-14	78-16019-02, Cisco IOS Release 12.2(18)SV2