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Understanding Spanning Tree Options in Aruba CX Switches

Joe Gehrke

Oct 3 2025

3 min read

In enterprise networks, Layer 2 redundancy is essential, but it introduces the risk of loops. Aruba CX switches support two primary Spanning Tree Protocol (STP) options to prevent loops while maintaining high availability:

Multiple Spanning Tree Protocol (MSTP)
Rapid Per-VLAN Spanning Tree Plus (RPVST+)

Each protocol has its strengths depending on your network’s size, complexity, and design goals.

MSTP (Multiple Spanning Tree Protocol)

Multiple-Instance Spanning Tree Protocol (MSTP) ensures that only one active path exists between any two nodes in a spanning-tree instance. A spanning-tree instance comprises a unique set of VLANs, and belongs to a specific spanning-tree region. A region can comprise multiple spanning-tree instances (each with a different set of VLANs), and allows one active path among regions in a network.

When to Use MSTP:

You have many VLANs and want to optimize traffic paths.
You need to scale your Layer 2 topology.
You want to reduce CPU load by aggregating VLANs into fewer STP instances.

Configuration:

switch(config)# spanning-tree mode mstp switch(config)# spanning-tree

Most small to medium configurations can be finished here, but if you need to configure different instances for separate VLANs, then you can refer to creating “spanning-tree instance vlan” in HPE’s documentation located here.

Verification:

switch# show spanning-tree mstp

RPVST+ (Rapid Per-VLAN Spanning Tree Plus)

RPVST+ is Aruba’s implementation of Cisco’s Rapid PVST+, offering a separate spanning tree instance for each VLAN. This provides the highest level of traffic optimization and fault isolation but increases CPU and memory usage.

When to Use RPVST+:

You need per-VLAN path control.
You’re integrating with Cisco networks using PVST+/RPVST+.
You want fast convergence and VLAN-level fault isolation.

Configuration:

switch(config)# spanning-tree mode rpvst switch(config)# spanning-tree spanning-tree vlan “List all vlans”

Set the core switch as the root switch for all vlans.

spanning-tree vlan “list all vlans” priority 5

The default priority is 8, so any priority lower than that will make that switch the root for that VLAN, assuming no other switch has a priority set lower (via manual configuration).

Verification:

switch# show spanning-tree rpvst

Choosing the Right Mode

Protocol	Convergence	VLAN Control	Scalability	Use Case
MSTP	Fast	Grouped VLANs	High	Large, VLAN-rich networks
RPVST+	Fast	Per-VLAN	Medium	Cisco integration, VLAN-specific tuning

Conclusion

Aruba CX switches offer flexible STP options to meet diverse network needs. MSTP is ideal for scalability and efficient resource use, while RPVST+ provides granular VLAN control and compatibility with Cisco environments. Choosing the right protocol ensures a loop-free, resilient, and optimized Layer 2 topology.

Have any questions which option works best for your environment? Please reach out to our IT experts at any time!

This publication contains general information only and Sikich is not, by means of this publication, rendering accounting, business, financial, investment, legal, tax, or any other professional advice or services. This publication is not a substitute for such professional advice or services, nor should you use it as a basis for any decision, action or omission that may affect you or your business. Before making any decision, taking any action or omitting an action that may affect you or your business, you should consult a qualified professional advisor. In addition, this publication may contain certain content generated by an artificial intelligence (AI) language model. You acknowledge that Sikich shall not be responsible for any loss sustained by you or any person who relies on this publication.

About the Author

Joe Gehrke

Joe has over 13 years of experience working in the IT industry. He started my career in a small computer repair shop and continued to evolve his skills to take on new responsibilities as a Help Desk Administrator, Systems Administrator, and at his current role as a Senior Network Consultant in Sikich’s Network Operation’s Center. He has certifications from VMware, Microsoft, and SonicWall.