Node election is based on leader election between the MSMs/MMs installed in the chassis, or master-capable nodes present in a SummitStack.
By default, the MSM/MM installed in slot A or the SummitStack node in slot 1 has primary status. Each node uses health information about itself together with a user configured priority value to compute its node role election priority. Nodes exchange their node role election priorities. During the node election process, the node with the highest node role election priority becomes the master or primary node, and the node with the second highest node role election priority becomes the backup node. All other nodes (if any) remain in STANDBY state.
The primary node runs the switch management functions, and the backup node is fully prepared to become the primary node if the primary fails. In SummitStack, nodes that remain in STANDBY state (called Standby nodes) program their port hardware based on instructions received from the primary. Standby nodes configured to be master-capable elect a new backup node from among themselves after a failover has occurred.
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