Cisco offers two major technologies for combining switches to improve scalability, redundancy, and manageability: StackWise (Stacking) and Virtual Switching System (VSS). While they both aim to simplify switch management and enhance resilience, they work in different ways and serve different use cases.
This article compares Cisco Stack and VSS in architecture, use cases, redundancy models, and operational differences to help you choose the right approach for your network design.
What Is Cisco StackWise?
Cisco StackWise is a switch-stacking technology commonly used in access layer designs. It allows multiple physical switches to operate as a single logical unit, managed through a single control and management plane.
Stackable via dedicated StackWise cables or StackWise Virtual (on supported models).
One switch acts as master; others function as members.
Configuration and software upgrades can be done centrally.
Supports up to 8–9 members in a single stack (varies by model).
Benefits:
Single IP management for all stack members.
Rapid failover with stack master redundancy.
Horizontal scalability in access layer deployments.
What Is Cisco VSS?
Virtual Switching System (VSS) is designed for core or distribution layer redundancy. It logically combines two physical chassis-based switches (like Catalyst 6500, 6800, or 4500) into one logical switch.
Key Characteristics:
Each chassis retains separate control and forwarding planes, but logically appears as one device.
Uses Multichassis EtherChannel (MEC) for link aggregation across both switches.
No Spanning Tree Protocol (STP) between VSS peers.
High-availability architecture for data center and campus core designs.
Benefits:
Simplifies Layer 2 topologies.
Enables dual-active forwarding.
No need for STP across VSS peers.
Faster convergence and increased throughput.
Cisco Stack vs VSS: Feature Comparison Table
Which One Should You Use?
Choose Cisco StackWise if:
You're deploying at the access layer.
You need easy configuration and scaling.
You want to manage multiple switches as one unit in a wiring closet.
Choose Cisco VSS if:
You need redundancy and high throughput at the core or distribution layer.
You want to eliminate STP issues.
You're working with chassis-based switches.
Newer Catalyst 9000 series switches also support StackWise Virtual, a hybrid between traditional stacking and VSS — ideal for higher-performance access or collapsed core designs.
FAQs
Q1: Can you stack switches in a VSS configuration?
No. VSS is used between two chassis-based switches and doesn’t support traditional stacking. However, newer platforms may offer StackWise Virtual, which combines the ideas of both.
Q2: What is StackWise Virtual?
StackWise Virtual allows two Catalyst 9500 or 9600 switches to operate as one, similar to VSS, but uses front-panel interfaces instead of a backplane or dedicated stack cables.
Q3: Does Cisco VSS replace stacking?
Not directly. VSS is suited for core/distribution layers, while stacking is better for access layer. Each has its use case based on topology needs.
Q4: Can StackWise provide the same redundancy as VSS?
To some extent. StackWise provides high availability within the stack, but lacks the scalability and MEC capabilities of VSS.
Q5: Which Cisco models support VSS?
VSS is primarily supported on Catalyst 4500, 6500, 6800, and some 9400/9600 series switches.
Conclusion
Cisco Stack and VSS both allow you to consolidate multiple switches, but they differ in purpose and implementation. StackWise is ideal for scaling access layers, while VSS provides high-availability at the core. Understanding the architecture, platform support, and operational needs of each technology is crucial for network design.
