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