KB.15.15

Figure 17 An MSTP network with legacy STP and RSTP devices connected

How MSTP operates

In the factory default configuration, spanning tree operation is off. Also, the switch retains its

currently configured spanning tree parameter settings when disabled. Thus, if you disable spanning

tree, then later re-enable it, the parameter settings will be the same as before spanning tree was

disabled. The switch also includes a "Pending"feature that enables you to exchange MSTP

configurations with a single command.

NOTE: The switch automatically senses port identity and type, and automatically defines spanning

tree parameters for each type, as well as parameters that apply across the switch. Although these

parameters can be adjusted, HP strongly recommends leaving these settings in their default

configurations unless the proposed changes have been supplied by an experienced network

administrator who has a strong understanding of the IEEE 802.1D/w/s standards and operation.

802.1s Multiple Spanning Tree Protocol (MSTP)

The switches covered in this guide use the IEEE 802.1s Multiple Spanning Tree Protocol (MSTP)

standard.

The 802.1D and 802.1w spanning tree protocols operate without regard to a network's VLAN

configuration, and maintain one common spanning tree throughout a bridged network. Thus, these

protocols map one loop-free, logical topology on a given physical topology. The 802.1s Multiple

Spanning Tree protocol (MSTP) uses VLANs to create multiple spanning trees in a network, which

significantly improves network resource utilization while maintaining a loop-free environment.

While the per-VLAN spanning tree approach adopted by some vendors overcomes the network

utilization problems inherent in using STP or RSTP, using a per-VLAN technology with multiple

About MSTP 121