Stack Merge and Split
Stack Merge
As shown in Figure 1-3, two stacks in the running state can merge into one stack. After two stacks merge, the master switches of the two stacks compete to be the master switch of the new stack (following the same master election rules used in a stack).
After the new master switch is elected, the member switches originally belonging to the same stack as this new master switch retain their roles and configurations, and their services are unaffected. Switches in the other stack restart and join the new stack.
Stack Split
After a stack is set up, the master and other member switches periodically send heartbeat packets to maintain the stack state. If a stack cable or member switch becomes faulty, communication between these member switches may be interrupted, and the stack may split into multiple stacks, as shown in Figure 1-4.
After a stack splits, member switches use the same global configuration. In this case, these switches use the same IP address and MAC address (stack MAC address) to communicate with other network devices. The address conflict causes a communication failure on the entire network. DAD can be configured to ensure that only one master switch exists after the stack splits.
