Follow the guidelines in the "Guidelines and Limitations for ISSU" section to ensure that the ISSU works smoothly.
Make sure that the network is stable and no changes are made while the ISSU is in progress.
Ensure feature compatibility between the current running release and the target release.
Make sure that interfaces are not in a spanning-tree designated forwarding state. Also, make sure that bridge assurance is not configured on any interface. The vPC peer-link is an exception to these requirements.
Verify that the current STP topology is consistent with the ISSU requirements. Use the show spanning-tree issu-impact command to display the STP configuration and whether or not there are potential STP issues.
Use the show lacp issu-impact command to display if a port or a peer switch is configured in the rate fast mode. The ISSU process is aborted if the system has any LACP fast timers configured.