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## Related Documentation

- Application Support for Stateful Line Module Switchover
- Log Messages Generated for Stateful LM Switchover
- Monitoring the Redundancy Status of Line Modules in a Specific Slot
- Monitoring the Redundancy History of Line Modules in a Specific Slot
- Interoperation of Redundancy and Stateful Switchover for Line Modules
- mode
- line-card switch
- show redundancy line-card
- show redundancy history

# Replacement of Line Modules When Stateful Line Module Switchover Is Enabled

You can use the show version command to view the status of the SRP modules and line modules, as well as the running and armed releases. The state field in the output of this command indicates whether the slot that contains the redundant line module indicates standby or is restarting. Any CLI or SNMP command that the system attempts to process at the time of restart or recovery of the line module might fail. If you configured the ha logging event category (using the log severity severityValue ha command), log messages are displayed to specify that the line module has warm restarted or cold started. Depending on the nature of failures, the line modules that participate in HA take the following actions:

## Reloading the Primary Line Module in Response to Failures

When a software fault occurs on the primary line module or if you enter the slot disable or reload slot commands for the slot in which the primary line module is installed, the secondary line module takes over by recovering all the applications running on the primary module to a stable state. After the secondary module takes over, traffic starts flowing through the secondary module. The FC and IOAs on the faulty line module are cold booted along with the IC. When you use the slot disable command for a slot that contains a line module, you disable only the line module; you do not disable the line module and IOAs associated with it.

## Reloading the Secondary Line Module in Response to Failures

When a software fault occurs on the secondary line module or if you enter the slot disable or reload slot commands for the slot in which the secondary line module is installed, the secondary line module undergoes a cold boot. After the secondary module becomes operational, the reloaded module continues to function as the secondary line module. Any core dumps that are generated on the faulty line module are sent to the SRP module, which is the same behavior as the one that occurs when a line module that is not configured for HA resets. When you use the slot disable command for a slot that contains a line module, you disable only the line module; you do not disable the line module and IOAs associated with it.

## Disabling the Primary and Secondary Line Module Slots

If you specify the slot erase command to delete the configuration of the module in the selected slot before you install a different type of module on slots that contain line modules that are members of a high availability pair, an error message states that you must deactivate high availability feature for the applicable line modules before erasing or replacing the slot configuration. You need to use the no mode high-availability slot command to disable high availability for the slots in which those line modules reside.

## Replacing Line modules Without Erasing the Slot Configuration

If you specify the slot replace command to replace an ES2 4G LM with a different type of module without erasing the interface configuration on slots that contain line modules that are members of a high availability pair, an error message is displayed. The error message indicates that you must deactivate high availability feature for the applicable line modules before erasing or replacing the slot configuration. You need to use the no mode high-availability slot command to disable high availability for the slots in which those line modules reside.

## Reloading the Router When Line Modules Enabled for HA Are Installed

If you enter the reload command on the router to restart the device with the currently available configuration, the previously configured roles of the primary and secondary line modules are preserved. SRP modules reload all line modules and restart form saved configuration files. However, any failure of the primary line module to become operational after the prescribed timeout duration causes the secondary module to take over as the primary.

## Removing IOAs Without Powering Down from Line Modules

Removal of an IOA from the primary line module without powering down the IOA does not trigger line module switchover. Removal of an IOA from the secondary line module does not cause the module to be cold started. In both such scenarios, we recommend that you perform a hot-swap of the IOA in a managed environment when high availability is configured on the line module pair.

## Cold and Warm Switchovers of Line Modules In a High Availability Pair

Cold switchover of the line module results in the same behavior as the system operations that are witnessed with line module redundancy configured on a router. With both these features, all the existing subscriber sessions are lost during the switchover.

When a warm switchover of the line module in a high availability pair occurs, subscriber sessions are not lost during the switchover.

## Related Documentation

- Application Support for Stateful Line Module Switchover
- Log Messages Generated for Stateful LM Switchover
- Monitoring the Redundancy Status of Line Modules in a Specific Slot
- Monitoring the Redundancy History of Line Modules in a Specific Slot
- Interoperation of Redundancy and Stateful Switchover for Line Modules
- mode
- line-card switch
- show redundancy line-card
- show redundancy history

#### Published: 2011-03-24

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