ZyXEL ES-3124PWR User Guide - Page 105

MST Region, 1.5.3, MST Instance

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Figure 52 MSTP Network Example A VLAN 1 VLAN 2 Chapter 11 Spanning Tree Protocol B 11.1.5.2 MST Region An MST region is a logical grouping of multiple network devices that appears as a single device to the rest of the network. Each MSTP-enabled device can only belong to one MST region. When BPDUs enter an MST region, external path cost (of paths outside this region) is increased by one. Internal path cost (of paths within this region) is increased by one when BPDUs traverse the region. Devices that belong to the same MST region are configured to have the same MSTP configuration identification settings. These include the following parameters: • Name of the MST region • Revision level as the unique number for the MST region • VLAN-to-MST Instance mapping 11.1.5.3 MST Instance An MST Instance (MSTI) is a spanning tree instance. VLANs can be configured to run on a specific MSTI. Each created MSTI is identified by a unique number (known as an MST ID) known internally to a region. Thus an MSTI does not span across MST regions. The following figure shows an example where there are two MST regions. Regions 1 and 2 have 2 spanning tree instances. ES-3124 Series User's Guide 105

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Chapter 11 Spanning Tree Protocol
ES-3124 Series User’s Guide
105
Figure 52
MSTP Network Example
11.1.5.2
MST Region
An MST region is a logical grouping of multiple network devices that appears as a single
device to the rest of the network. Each MSTP-enabled device can only belong to one MST
region. When BPDUs enter an MST region, external path cost (of paths outside this region) is
increased by one. Internal path cost (of paths within this region) is increased by one when
BPDUs traverse the region.
Devices that belong to the same MST region are configured to have the same MSTP
configuration identification settings. These include the following parameters:
Name of the MST region
Revision level as the unique number for the MST region
VLAN-to-MST Instance mapping
11.1.5.3
MST Instance
An MST Instance (MSTI) is a spanning tree instance. VLANs can be configured to run on a
specific MSTI. Each created MSTI is identified by a unique number (known as an MST ID)
known internally to a region. Thus an MSTI does not span across MST regions.
The following figure shows an example where there are two MST regions. Regions 1 and 2
have 2 spanning tree instances.
A
B
VLAN 1
VLAN 2