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Stack Upgrade
A stack can be upgraded using the traditional upgrade method (by specifying the next-startup files and restarting the entire stack) or the fast upgrade function:
Traditional upgrade: You need to specify next-startup files and restart the entire stack. This method causes lengthy service interruptions and is not applicable to scenarios requiring short service interruptions.
Fast upgrade: This upgrade method provides a mechanism to minimize the service interruption time during software upgrade of stack member switches, reducing impact of the upgrade on services.
Figure 1-26 shows the fast stack upgrade process:- Before the upgrade, downstream and upstream devices are dual-homed to the stack using Eth-Trunks. If this connection mode is not used, there will be a lengthy traffic interruption during the upgrade.
- During the upgrade, the standby switch first restarts with the new system software. After the upgrade is complete, data traffic is forwarded by the master switch.
- After the standby switch is upgraded, it becomes the new master switch and starts to forward data traffic. Then the original master switch restarts with the new system software. After the upgrade is complete, the original master switch becomes the new standby switch in the stack.
- After the upgrade is complete, data traffic is forwarded normally.
During a fast upgrade, if the standby switch cannot be upgraded due to faults such as upgrade timeout, stack link faults, and card registration failures, the standby switch will roll back to the previous version. After the standby switch is upgraded successfully, the stack cannot roll back to the previous version.During a fast stack upgrade, if the original master switch fails to join the stack because of a stack link fault, you need to restart the original master switch after the stack link recovers so that the original master switch can join the stack again.
