Stateful Line Module Switchover States

The line module progresses through various high availability states. These states are illustrated in Figure 5.

Figure 5: Stateful Line Module Switchover States

Stateful Line Module
Switchover States

Disabled State

The initial, default state for high availability mode is disabled. While in this state, the router continues to use redundancy mode. If a switchover occurs while the router is in this state, the standby line module performs a cold switchover.

The router enters this state when you power up the router or when the router warm-restarts from a stateful line module switchover. After you enable high availability, the system must meet the following criteria before it can enter the initializing state:

During the disabled state:

The behavior of the router depends on which HA state the application is in when it shifts to a disabled state:

Note: You can use the show redundancy line-card command to display the name of any unsupported applications that are configured.

While in the disabled state, the system operates as if it were configured for redundancy functionality.

If all criteria are met, high availability mode transitions to the initialization state.

Initializing State

After the line module transitions into the initializing state, bulk synchronization of the memory occurs. This activity consists of mirroring of appropriate state and dynamic configuration information from the active line module (memory) to the standby line module (memory). Depending on the size of the configuration, this process can take several minutes.

During the initializing state:

Active State

During the active state, the data that was synchronized from the active line module to the standby line module during initialization remains synchronized through mirroring updates.

Mirroring updates occur as follows:

  1. When making changes or updates, applications create individual transactions, perform the updates on the active line module, and post the transactions.
  2. Following the updates, the active line module sends the changes to the standby line module.
  3. The standby line module replays the updates (in the order in which they were committed on the active line module) and makes the appropriate changes for each changed application.

During the active state:

After the stateful line module switchover process transitions to the active state, the information to be mirrored on the standby module is sent immediately from the primary line module when bulk synchronization of data is not in progress from the primary to the secondary module. This mirroring operation occurs even when the buffer is not completely full in the storage containers.

Related Documentation