Configuring Spanning Tree Protocol (STP)

When PVST is enabled on an HP port, that port sends BPDUs in PVST format instead of HP’s spanning tree format.

PVST+

HP devices and Cisco devices support separate spanning trees on an individual port-based VLAN basis. However, until the IEEE standard for multiple spanning trees is finalized, vendors are using different methods to support multiple spanning trees within their own products. PVST+ is an extension to PVST that enables a Cisco device to interoperate with other devices that are running a single spanning tree (IEEE 802.1Q) while still running a separate spanning tree in each VLAN.

PVST+ uses 802.1Q single STP BPDUs on VLAN 1 and PVST BPDUs (which have a proprietary format) for other VLANs. In this case, the Cisco device uses devices running 802.1Q as tunnels for PVST (non-802.1Q) traffic. The 802.1Q single STP BPDUs are addressed to the well-known STP MAC address 01-80-C2-00-00-00. The PVST BPDUs for the other VLANs are addressed to multicast address 01-00-0C-CC-CC-CD.

The PVST+ method can require manual configuration of STP parameters on the 802.1Q devices to ensure that traffic for the PVST VLANs is not blocked. In addition, the opportunities to adjust STP parameters to load balance traffic on a VLAN basis are limited when using PVST+.

Using HP Single STP with Cisco PVST+

Since HP’s single STP feature complies with IEEE 802.1Q (the single STP specification), you also can use an HP device running single STP to interoperate with a Cisco device running PVST+. When you enable single STP on an HP device, the PVST compatibility feature is not enabled, even if a port receives a PVST BPDU.

Enabling PVST/PVST+ Statically

PVST/PVST+ support is automatically enabled on a port if the port receives a BPDU in PVST/PVST+ format. However, you can statically enable PVST/PVST+ support on a port if desired. In this case, the support is enabled immediately and support for HP tagged BPDUs is disabled at the same time. To enable the PVST/PVST+ support, use the following CLI method.

NOTE: When PVST/PVST+ support is enabled on a port, support for HP BPDUs is disabled.

USING THE CLI

To enable PVST/PVST+ support on a port, enter commands such as the following:

HP9300(config)# interface ethernet 1/1

HP9300(config-if-1/1)# pvst-mode

Syntax: [no] pvst-mode

NOTE: If you disable PVST/PVST+ support, the software still automatically enables PVST/PVST+ support if the port receives an STP BPDU with PVST/PVST+ format.

USING THE WEB MANAGEMENT INTERFACE

You cannot enable PVST support using the Web management interface.

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