Stack Setup Process

A stack is set up after the following stages:

1. Physical connection and software configuration: Based on network requirements, users select a proper connection topology to set up a stack and configure related software.
2. Master election: Member switches exchange stack competition packets and elect a master switch according to master election rules.
3. Topology collection: The master switch collects information about all the member switches and calculates the topology. If some member switches have the same stack member ID, the master switch reassigns stack member IDs to the member switches.
4. Running: The master switch synchronizes the topology of the entire stack to all the member switches and selects a standby switch.

Role Election

After a stack is set up, member switches exchange stack competition packets to elect a master switch. The member switches compare the following items in the listed order to elect the master switch (the election ends when a winning switch is found):

1. Running status: The switch that completes startup becomes the master switch.
2. Stack priority: The switch with the highest stack priority becomes the master switch.
3. Software version: The switch running the latest software version becomes the master switch.
4. (Only on CE12800&12800E series switches) Number of main processing units (MPUs): The switch with two MPUs is preferred over the switch with only one MPU.
5. Bridge MAC address: The switch with the smallest bridge MAC address becomes the master switch.

Topology Collection

After a master switch is elected, it collects information about all the member switches and calculates the topology. If some member switches have the same stack member ID, the master switch reassigns stack member IDs to the member switches.

Stable Running

After the master switch completes topology calculation, it synchronizes the topology of the entire stack to all the member switches and selects a standby switch. The master switch compares the following items of member switches in the listed order to select the standby switch (the election ends when a winning switch is found):

1. Stack priority: The switch with the highest stack priority becomes the standby switch.
2. Bridge MAC address: The switch with the smallest bridge MAC address becomes the standby switch.

Software Version Synchronization

A stack supports software version synchronization among the member switches. The member switches do not have to run the same software version, and they can set up a stack as long as their software versions are compatible with each another. If software version running on a member switch is different from that on the master switch, the member switch downloads the system software from the master switch, restarts with the new system software, and rejoins the stack.

Configuration File Synchronization

A stack uses a strict configuration file synchronization mechanism to ensure that the member switches work like one device.

• When a stack is set up, each member switch starts with its own configuration file. After switches start, the standby and slave switches combine their stack configurations into the configuration file of the master switch to form the configuration file of the stack system.
• When the stack is running normally, the master switch manages the entire stack, and synchronizes configurations made by users to the other switches in real time to maintain configuration consistency on all the member switches.

The configuration file synchronization mechanism ensures that the member switches save the same configuration file. If the master switch fails, other member switches can provide services using the same configuration file.