Best Practices

When you are planning to perform a unified in-service software upgrade (unified 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.
• During a unified ISSU, you cannot bring any PICs online or offline.