ISSU Limitations and Considerations
When using ISSU, consider the following capabilities and restrictions:
- ISSU is supported on FastIron stackable hardware.
- ISSU is supported in a traditional ring stack topology.
- ISSU works for stacks of two units to the maximum supported twelve units.
- ISSU is supported for upgrades between minor releases only. For example, you can use ISSU to upgrade between FastIron 08.0.90 and FastIron 08.0.90a or between FastIron 08.0.90a and subsequent patch releases, but not between FastIron 09.0.10a and FastIron 10.0.00.
- For ISSU to occur with minimal disruption, the customer network connected to the stack must have redundant uplink and downlink configurations across multiple units.
- If the secondary partition is upgraded, this secondary partition is set as the default boot partition for the stack.
- Most CLI commands, SNMP, and web operations are blocked while ISSU is in progress.
- To make the upgrade seamless, the following administrative operations are blocked while ISSU is in progress:
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During reload from the active stack unit, if there is a unit within the stack with a different image, access to that unit could be lost. Beginning with FastIron release 10.0.20, when using the
reloadcommand, the process will automatically include an image consistency check. If a mismatch is found, an error message will show a list of mismatched units and the reload procedure stops. You should copy the required image and make sure all devices have the same image before attempting another reboot.