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!
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