Brocade FastIron Ethernet Switch Stacking Configuration Guide - Manual (Page 110)

• Internal switchover resulting from a priority change is blocked until the entire stack is reloaded or
hitless stacking is enabled. A priority change will trigger an election, but the newly elected winner
will not immediately assume its role.
• If there is no active controller after a reload, the bootup standby will assume the active role after
reloading every unit in the stack, including itself.
• During a stack merge, the active controller with the highest priority will win the election and reload
every unit of the losing stack.
NOTE
Synchronization between the active controller, standby controller, and stack members will occur
whether or not hitless stacking is enabled.
Hitless stacking is disabled by default. To enable it, enable hitless stacking failover When hitless
stacking is enabled, the following behavior takes effect immediately:
• If a failover occurs, the stack will not reload.
• Manual switchover (CLI command stack switch-over) is allowed.
• If a priority change occurred while hitless stacking was disabled, and the configured priority value
requires a switchover, the system will start a 60-second timer before performing a switchover.
After the switchover, the highest priority standby will become the active controller.
• If there is no active controller after a reload, the bootup standby will assume the active role in
approximately 90 seconds without a reload.
• During a stack merge, the active controller with the larger number of units will win the election and
reload every unit of the losing stack. If two stacks have the same number of units, then the
priority, system up time, ID, then MAC address is compared. If two stacks have the same number
of units and the same priority, then the stack with the longest system up-time (by 30 seconds or
more) will win the election. Otherwise, the smallest ID is compared next, followed by MAC
address. If the losing active controller has the highest priority, it will become a standby after
reloading and relearning the protocols. Finally, it will become the active controller after an internal
switchover.
NOTE
If the active controllers of two merging stacks have different hitless stacking settings (for example,
hitless stacking is enabled in one stack and disabled in the other), the default behavior (hitless
stacking disabled) will be used in the stack merge. After the merge, the winner will retain its hitless
stacking setting and runtime configuration for the merged stack.
You can use the show stack command to view whether or not hitless stacking is enabled.
Enabling hitless stacking
Hitless stacking is disabled by default. To enable it, enable hitless stacking failover as described in
“Enabling hitless stacking failover.”
Displaying hitless stacking status
You can use the show stack command to view whether or not hitless stacking is enabled. The
following example shows that hitless stacking is disabled.
device#show stack
alone: standalone, D: dynamic config, S: static config
ID Type Role MAC Address Pri State Comment
2 S FCX648S member 0000.0000.0000 0 reserve
3 S FCX624 member 0000.0076.2640 0 remote Ready
5 S FCX624 standby 0000.0000.0400 100 remote Ready
Enabling hitless stacking
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