C a u t i o n

N o t e

Multiple Instance Spanning-Tree Operation

802.1s Multiple Spanning Tree Protocol (MSTP)

MSTI must initially exist in the IST instance of the same MST region. When you assign a static VLAN to an MSTI, the switch removes the VLAN from the IST instance. (Thus, you can assign a VLAN to only one MSTI in a given region.) All VLANs in an MSTI operate as part of the same single spanning tree topology. (The switch does not allow dynamic VLANs in an MSTI.)

When you enable MSTP on the switch, the default MSTP spanning tree configuration settings comply with the values recommended in the IEEE 802.1s Multiple Spanning Tree Protocol (MSTP) standard. Note that inappropriate changes to these settings can result in severely degraded network performance. For this reason, ProCurve strongly recommends that changing these default settings be reserved only for experienced network administrators who have a strong understanding of the IEEE 802.1D/w/s standards and operation.

How MSTP Operates

In the factory default configuration, spanning tree operation is on. 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. (Refer to “Enabling an Entire MST Region at Once or Exchanging One Region Configuration for Another” on page 4-40.)

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, ProCurve 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.

MST Regions

All MSTP switches in a given region must be configured with the same VLANs. Also, each MSTP switch within the same region must have the same VLAN-to- instance assignments. (A VLAN can belong to only one instance within any region.) Within a region:

■All of the VLANs belonging to a given instance compose a single, active spanning-tree topology for that instance.

■Each instance operates independently of other regions.

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