Spanning Tree Configuration - Motorola WiNG 5 System Reference Manual

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5.3.5.6 Spanning Tree Configuration

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Profile Network Configuration
The Multiple Spanning Tree Protocol (MSTP) provides an extension to RSTP to optimize the usefulness o f VLANs.
MSTOP allows for a separate spanning tree for each VLAN group, and blocks all but one of the possible alternate
paths within each spanning tree topology.
If there's just one VLAN in the access point managed network, a single spanning tree works fine. However, if the
network contains more than one VLAN, the network topology defined by single STP would work, but it's possible to
make better use of the alternate paths available by using an alternate spanning tree for different VLANs or groups of
VLANs.
A MSTP supported deployment uses multiple MST regions with multiple MST instances (MSTI). Multiple regions and
other STP bridges are interconnected using one single common spanning tree (CST).
MSTP includes all of its spanning tree information in a single Bridge Protocol Data Unit (BPDU) format. BPDUs are
used to exchange information bridge IDs and root path costs. Not only does this reduce the number of BPDUs required
to communicate spanning tree information for each VLAN, but it also ensures backward compatibility with RSTP.
MSTP encodes additional region information after the standard RSTP BPDU as well as a number of MSTI messages.
Each MSTI messages conveys spanning tree information for each instance. Each instance can be assigned a number
of configured VLANs. The frames assigned to these VLANs operate in this spanning tree instance whenever they are
inside the MST region. To avoid conveying their entire VLAN to spanning tree mapping in each BPDU, the access point
encodes an MD5 digest of their VLAN to an instance table in the MSTP BPDU. This digest is used by other MSTP
supported devices to determine if the neighboring device is in the same MST region as itself.
To define the spanning tree configuration:
1. Select the
2. Select Devices.
3. Select System Profile
4. Expand the
Configuration tab from the Web UI.
from the options on left-hand side of the UI.
Network menu and select Spanning Tree