Software Requirements for Unified ISSU

• The running JUNOSe software release must support unified ISSU.

  You can upgrade to a software version that supports unified ISSU from a software version that does not support unified ISSU only by means of a conventional upgrade. During the conventional upgrade, all line modules are reloaded, all subscribers are dropped, and traffic forwarding is interrupted until the upgrade is completed.

• The armed (upgrade) release must be capable of being upgraded to from the currently running release; it must be higher-numbered than the running release.
• All applications that are configured on the router must support unified ISSU and stateful SRP switchover.

  If one or more unified ISSU-challenged applications are configured and you proceed with a unified in-service software upgrade, the unified ISSU process forces a conventional upgrade on the router. All line modules are reloaded, all subscribers are dropped, and traffic forwarding is interrupted until the upgrade is completed.

  You can avoid this circumstance by removing the configuration for the unified ISSU-challenged applications from the router before you begin the in-service software upgrade.

  See Application Support for Unified ISSU for information about whether an application supports unified ISSU.

• Stateful SRP switchover must be configured on the router. Use the following commands to configure high availability:

  host1(config)#redundancy

  host1(config-redundancy)#mode high-availability

   

  See Managing Modules for information about high availability.

The following requirements must be met for traffic forwarding to continue. However, failing to meet these requirements does not halt the unified ISSU operation. The unified ISSU process offers the option to override or ignore these forwarding requirements.

• Graceful restart must be enabled for all configured routing protocols. The unified ISSU operation relies on graceful restart to keep the routing protocols alive through the various stages of the upgrade.
• All connected peers must be configured with graceful restart. Because some protocols cannot themselves confirm peer configuration for graceful restart, you must ensure that the peers are properly configured.
• For applications that exchange keepalive messages with peers, you must ensure that the poll times are adequate to maintain the peering session across any forwarding interruption caused by the unified ISSU operation.
• On the ERX-1440, you must enter the key provided with your license in order to make the unified ISSU CLI commands available. Unified ISSU is licensed on only the ERX-1440 router; no license is required or available on the E120 and E320 routers.

  The license issu command is available only on the ERX-1440 CLI.

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