HP ProCurve J8766A Release Note page 104

Enhancements
Release L.11.08 Enhancements
Overview
The MSTP VLAN Configuration enhancement allows you to preconfigure an MSTP regional topology
and ensure that the same VLAN ID-to-MSTI assignments exist on each MSTP switch in the region.
The default behavior of the spanning-tree instance vlan command changes so that, before a static
VLAN is configured or a dynamic VLAN is learned on the switch, you can preconfigure its VLAN ID-
to-MSTI mapping. Later, when the VLAN is created, it is automatically assigned to the MSTI to which
you had previously mapped it.
By supporting preconfigured VLAN ID-to-MSTI topologies, the VLAN Configuration enhancement
provides the following benefits:
Scalability: In a network design in which you plan to use a large number of VLANs, you can
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preconfigure identical VLAN ID-to-MSTI mappings on all switches in a single, campus-wide MST
region, regardless of the specific VLANs that you later configure on each switch. After the initial
VLAN ID-to-MSTI mapping, you can decide on the exact VLANs that you need on each switch.
All switches in a region must be configured with the same VLAN ID-to-MSTI mappings and the
same MSTP configuration identifiers (region name and revision number).
Flexibility: By preconfiguring identical VLAN ID-to-MSTI mappings on all switches in an MST
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region, you can combine switches that support different maximum numbers of VLANs.
■ Network stability: You can reduce the interruptions in network connectivity caused by the
regeneration of spanning trees in the entire network each time a configuration change in VLAN-
to-MSTI mapping is detected on a switch. The negative impact on network performance is
reduced if all newly created VLANs are pre-mapped to the correct MST instances. Later, VLAN
creation and deletion are ignored by MSTP and no interruption in spanning-tree traffic occurs.
Usability: Dynamically learned GVRP VLANs can be mapped to MSTIs and support MSTP load
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balancing.
PreConfiguring VLANs in an MST Instance
When you configure an MSTP regional topology, you create multiple spanning-tree instances. Each
MST instance provides a fully connected active topology for a particular set of VLANs.
Each switch in an MSTP region is configured with the following set of common parameters:
Region name (spanning-tree config-name)
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Region revision number (spanning-tree config-revision)
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Identical VLAN ID-to-MSTI mapping (spanning-tree instance vlan)
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Each MST instance supports a different set of VLANs. A VLAN that is mapped to an MST instance
cannot be a member of another MST instance.
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