Defining Multiple Spanning Tree - Alcatel OS-LS-6224 User Manual

3
Configuring the Switch

Defining Multiple Spanning Tree

Multiple Spanning Tree (MSTP) provides differing load balancing scenarios. For
example, while port A is blocked in one STP instance, the same port can be placed
in the Forwarding state in another STP instance. The MSTP General Page contains
information for defining global MSTP settings, including region names, MSTP
revisions, and maximum hops.
MSTP generates a unique spanning tree for each instance. This provides multiple
pathways across the network, thereby balancing the traffic load, preventing
wide-scale disruption when a bridge node in a single instance fails, and allowing for
faster convergence of a new topology for the failed instance.
By default all VLANs are assigned to the Internal Spanning Tree (MST Instance 0)
that connects all bridges and LANs within the MST region. This switch supports up
to 16 instances. You should try to group VLANs which cover the same general area
of your network. However, remember that you must configure all bridges within the
same MSTI Region with the same set of instances, and the same instance (on each
bridge) with the same set of VLANs. Also, note that RSTP treats each MSTI region
as a single node, connecting all regions to the Common Spanning Tree.
Command Attributes
• Region Name — User-defined STP region name.
• Revision — An unsigned 16-bit number that identifies the revision of the current
MSTP configuration. The revision number is required as part of the MSTP
configuration. The possible field range is 0-65535.
• Max Hops — Specifies the total number of hops that occur in a specific region
before the BPDU is discarded. Once the BPDU is discarded, the port information
is aged out. The possible field range is 1-40. The field default is 20 hops.
—
• IST Master
specified instance root.
Web – Click Layer 2, Spanning Tree, MSTP, General. Define the fields and Click
Apply.
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Identifies the Spanning Tree Master instance. The IST Master is the