Users Guide

Table Of Contents
Dell Networking W-Series ArubaOS 6.5.x | User Guide PVST+ | 639
Chapter 26
PVST+
PVST+ (Per-VLAN Spanning Tree Plus) provides load-balancing of VLANs across multiple ports, resulting in
optimal usage of network resources. PVST+ also ensures interoperability with industry-accepted PVST+
protocols.
PVST+ is disabled by default.
Topics in this chapter include:
l Understanding PVST+ Interoperability and Best Practices on page 639
l Enabling PVST+ in the CLI on page 639
l Enabling PVST+ in the WebUI on page 640
Understanding PVST+ Interoperability and Best Practices
Interoperability between RSTP and PVST+ includes:
l When the access port on the controller and the trunk port terminate on one Layer 2 switch running PVST+,
PVST+ sends untagged STP BPDUs on the access port; it also transmits untagged STP BPDUs (in addition to
the other PVST+ BPDUs) on the native VLAN trunk port. If the Dell controller is the root, it detects a loop on
the native VLAN.
If PVST+ is not on the controller, best practices recommend disabling RSTP on the Dell controller to avoid a looping
issue.
l For VLAN load balancing when controllers are connected to armed mode, the VLAN priorities on two ports
and bridge priorities must be configured so that one set of VLANs are active on one link, and the other set
of VLANs are active on the other link.
l 64 instances are supported on the W-7000 Series and W-7200 Series controllers.
Enabling PVST+ in the CLI
PVST+ is disabled by default. Enable PVST+, ensure a VLAN instance is configured, and then configure PVST+.
1. Enable PVST+:
spanning-tree mode rapid-pvst
2. Configure PVST+ forward time; the following command sets the time VLAN 2 spends in the listening and
learning state (3 seconds):
spanning-tree vlan 2 forward-time 3
3. Configure PVST+ hello time; the following command sets the time VLAN 2 waits to transmit BPDUs to four
seconds:
spanning-tree vlan 2 hello-time 4
4. Configure PVST+ max age; the following command sets the time VLAN 2 waits to receive a hello packet to
30 seconds:
spanning-tree vlan 2 max-age 30