PVST/PVST+ Compatibility

The FastIron family of switches support Cisco's Per VLAN Spanning Tree plus (PVST+) protocol, by allowing the device to run multiple spanning trees while also interoperating with IEEE 802.1Q devices1.

Note: RUCKUS device ports automatically detect PVST+ BPDUs and enable support for the BPDUs once detected. You do not need to perform any configuration steps to enable PVST+ support.

Support for Cisco's PVST+ protocol allows a RUCKUS device to run multiple spanning trees while also interoperating with IEEE 802.1Q devices. RUCKUS device ports automatically detect PVST+ BPDUs and enable support for the BPDUs once detected. The enhancement allows a port that is in PVST+ compatibility mode due to auto-detection to revert to the default multiple spanning trees mode when one of the following events occurs:

  • The link is disconnected or broken
  • The link is administratively disabled
  • The link is disabled by interaction with the link-keepalive protocol

This enhancement allows a port that was originally interoperating with PVST+ to revert to multiple spanning trees when connected to a RUCKUS device.

  1. Cisco user documentation for PVST/PVST+ refers to the IEEE 802.1Q spanning tree as the Common Spanning Tree (CST). ↩

In this section:

  1. Overview of PVST and PVST+
  2. Configuring PVST+ Support
  3. Displaying PVST+ Support Information
  4. PVST+ Configuration Examples
  5. PVST+ Protect
    If a PVST+ packet is received on a port configured for Multiple Spanning Tree Protocol (MSTP), the RUCKUS device floods it to all its ports in the VLAN so that it reaches other PVST+ devices across the VLAN. This flooding can sometimes cause a port to be blocked on the Cisco side. Use the PVST+ Protect feature to prevent this flooding, blocking the PVST+ BPDU and marking the port as ERR-DISABLED.