Reference Guide

876 | Stacking
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Merging Two Stacks
You can merge two S5000 switch stacks while they are powered and online. To merge two stacks, connect
one stack to the other using port cables. After you connect the port cables, a merge of the two stacks is
performed:
• FTOS selects a master switch for the merged stack from the existing masters in the two stacks.
To ensure that one of the two master switches wins the master election in the merged stack, use the
stack-unit priority command to configure the highest priority for the unit (refer to Assigning a Priority to
Stacked Switches).
• All the units in the losing stack reboot and then merge with the winning stack that has the stack master.
• If there is no unit numbering conflict, the stack members retain their previous unit numbers.
Otherwise, the stack master assigns new unit numbers, based on the order in which they come online.
• The new stack master uses its own startup and running configurations to synchronize the
configurations on the new stack members.
Splitting a Stack
To split an S5000 stack, unplug the port cables between member units at any time: while the stack is
powered on or off and when the units are online or offline. Each portion of the split stack retains the startup
and running configuration of the original stack.
For a stack that is split into two smaller stacks, each with multiple units:
• If one of the new stacks receives the master and standby units, it is unaffected by the split.
• If one of the new stacks receives only the master unit, the master switch retains its role and a new
standby is elected.
• If one of the new stacks receives only the standby unit, it becomes the master in the new stack and
FTOS elects a new standby.
FTOS Behavior: When you add a new switch to a stack:
• When a unit is added to a stack, the management unit performs a system check on the new unit to
ensure the hardware type (S5000) is compatible. A similar check is performed on the FTOS ver-
sion. If the stack is running 9.0(1.3) and a new unit is running a different software version, the new
unit is put into a card problem state. The new unit is then upgraded to use the same FTOS version
as the stack and is rebooted before joining the stack.
• If the new unit has been configured with a stack number that is already assigned to a stack mem-
ber, the stack avoids a numbering conflict by assigning the new switch the first available stack
number.
• After the new unit loads, it synchronizes its running and startup configurations with the stack.
Note: Adding a new unit that is powered on and has stack groups configured is the same as merging two
stacks (see Adding a Stack Unit). If the new unit has been configured with a higher priority than the
current stack master, it becomes the new stack master and the stack reloads. If the new unit does not
have a higher priority than the master switch, it reboots and is added as a member switch.