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 master 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.