When your stack is operational, one switch is the primary switch, responsible for running network protocols and managing the stack.
To provide recovery in case of a break in the stack connections, you can configure redundancy by designating a backup switch to take over as primary if the primary switch fails. When you perform the initial software configuration of the stack, the “easy setup” configuration option automatically configures redundancy, with slot 1 as the primary and slot 2 as the backup. You can also configure additional switches as “primary-capable,” meaning they can become a stack primary in case the initial backup switch fails.
When assigning the primary and backup roles in mixed stacks, consider the feature scalability and the speed of each switch model. The easy setup configuration process selects primary and backup switches based on capability and speed. The following list shows the capabilities based on the ability to cross stack with other switch families. The most capable switches are shown at the top of each list:
5420 Series switches can be stacked with themselves, or with 5320 Series or 5520 Series switches using Alternate stacking. The 5320 Series can only act as a Standby node in a 5420 Series Primary configuration. The 5320 Series cannot act as a Backup node when the Primary node is a 5420 Series.
Beginning with Switch Engine 31.5, 5420 Series switches can be stacked with the 5520 Series switches using SummitStack-V80 and a special cable which converts QSFP+ to SFP-DD. The SummitStack-V80 configuration sets the speed of the QSFP+ stack ports to 20Gb.
When easy setup compares two switches that have the same capability, the lower slot number takes precedence.
Follow the same ranking hierarchy when you plan the physical placement of the switches in the stack.