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Best Practices for Performing a Unified ISSU

When you are planning to perform a unified in-service software upgrade (ISSU), choose a time when your network is as stable as possible. As with a normal upgrade, Telnet sessions, SNMP, and CLI access are briefly interrupted. In addition, the following restrictions apply:

  • The primary Routing Engine and backup Routing Engine must be running the same software version before you can perform a unified ISSU.

  • Verify that your platform supports the unified ISSU feature.

  • Read the “Unified ISSU Considerations” topic in the chapter Unified ISSU System Requirements to anticipate any special circumstances that might affect your upgrade.