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# Halting the Unified ISSU Process and Restoring the Original State of the Router

The options that are available to halt the in-service software upgrade depend on the phase that the upgrade is in when you attempt to halt it. The phase also affects the state of the router after the upgrade is halted.

## Halting Unified ISSU During Initialization Phase

During the initialization phase, you can halt the unified ISSU process by issuing the issu stop command. This action reloads the redundant SRP module with the armed upgrade release. As a result, unified ISSU is placed in the idle state and the following releases are present on the router:

- Primary SRP module—Running (original) release
- Redundant SRP module—Upgrade release
- Line modules—Running (original) release

After you stop unified ISSU, you can return the router to the state it was in when you began the in-service software upgrade. To roll the router back to its beginning state with the redundant SRP module running the original release, you must perform the following steps to arm the redundant SRP module with the running release:

1. Turn off auto synchronization.
   `
   host1(config)#disable-autosync
   `
2. Specify that the router use the running release when it reboots.
   `
   host1(config)#boot system erx_x-y-z.rel
   `
3. Synchronize the NVS file system of the redundant module with that of the primary module.
   `
   host1#synchronize
   `

   The redundant SRP module automatically reboots because the armed release (the original release) now differs from the software release it is currently running (the upgrade release).

4. Verify that stateful SRP switchover is enabled.
   `
   host1#show redundancy
   `

## Halting Unified ISSU During Upgrade Phase

During the upgrade phase—before the line module and control plane software is upgraded—the unified ISSU process provides an opportunity to cancel the upgrade. If you choose to cancel, the router remains in the unified ISSU initialized state. The CLI command set becomes fully accessible.

If you do not cancel at this point, then the process continues and any line modules that do not support unified ISSU are reloaded. Application sessions are brought down and traffic forwarding is interrupted for the unsupported modules.

If you do cancel in response to the CLI prompt, unified ISSU returns to the initialized state, and the following releases are present on the router:

- Primary SRP module—Running (original) release
- Redundant SRP module—Upgrade release; the module is in the unified ISSU initialized state
- Line modules—Running (original) release

To roll back from the unified ISSU initialized state, you must issue the issu stop command. The command reloads the redundant SRP module with the armed release and places unified ISSU in the idle state. As a result, the following releases are present on the router:

- Primary SRP module—Running (original) release
- Redundant SRP—Upgrade release
- Line modules—Running (original) release

After you stop unified ISSU, you can return the router to the state it was in when you began the in-service software upgrade. To roll the router back to its beginning state with the redundant SRP module running the original release, you must perform the following steps to arm the redundant SRP module with the running release:

1. Turn off auto synchronization.
   `
   host1(config)#disable-autosync
   `
2. Specify that the router use the running release when it reboots. For
   `
   host1(config)#boot system erx_x-y-z.rel
   `
3. Synchronize the NVS file system of the redundant module with that of the primary module.
   `
   host1#synchronize
   `

   The redundant SRP module automatically reboots because the software release that it is configured to run now differs from the software release it is running.

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