Stacking two core switches

You can stack two core switches using dedicated stack ports or StackWise Virtual to operate as a single logical switch with redundancy and centralized management.

Overview of Switch Stacking

Stacking allows multiple physical switches to function as a single logical switch, simplifying management, increasing redundancy, and aggregating bandwidth between switches . In a two-switch stack, one switch is designated as the active (master) and the other as the standby, ensuring seamless failover if the active switch fails . StackWise Virtual extends this concept by connecting two physical switches via a StackWise Virtual Link (SVL), synchronizing control plane information and providing high availability .

Physical Setup

1. Verify Compatibility: Ensure both switches are stack-capable and running the same IOS version and feature set .
2. Connect Stack Cables: Use the dedicated stack ports on the back of each switch. For StackWise Virtual, connect the two switches using the SVL interfaces .
3. Power On Sequence: Power on the switch intended to be the master first, then power on the second switch. This ensures proper stack member numbering and master election .
4. Topology: For two switches, a simple ring topology is recommended to provide redundancy, though a single link is sufficient for basic stacking .

Configuration Steps

1. Assign Stack Priorities: Configure the priority for each switch to influence which becomes the active switch. Higher priority increases the likelihood of being elected master. Default priority is 1; values range from 1 to 15 .
2. Verify Stack Membership: Use commands like show switch or show switch detail to confirm stack member numbers and roles .
3. Enable StackWise Virtual (Optional): On supported models (e.g., Cisco C9500), configure StackWise Virtual to combine the two switches into a single logical device with redundant control planes .
4. Dual-Active Detection: Configure the DAD interface to prevent both switches from acting as active devices in case of SVL failure .

Best Practices

• Firmware Consistency: Ensure both switches run the same firmware to avoid stack instability .
• Document Stack Configuration: Record stack member numbers, priorities, and cable connections for troubleshooting .
• Redundancy: Use a ring topology or StackWise Virtual to maintain connectivity if a stack cable fails .
• Monitor Stack Health: Regularly check stack status using show switch and monitor for any member failures . By following these steps, you can successfully stack two core switches, achieving centralized management, high availability, and simplified network operations.