ZyXEL GS2200-8 User Guide - Page 126

MSTP Network Example, MST Region

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Chapter 13 Spanning Tree Protocol 13.10.1 MSTP Network Example The following figure shows a network example where two VLANs are configured on the two switches. If the switches are using STP or RSTP, the link for VLAN 2 will be blocked as STP and RSTP allow only one link in the network and block the redundant link. Figure 78 STP/RSTP Network Example A VLAN 1 VLAN 2 B With MSTP, VLANs 1 and 2 are mapped to different spanning trees in the network. Thus traffic from the two VLANs travel on different paths. The following figure shows the network example using MSTP. Figure 79 MSTP Network Example A VLAN 1 VLAN 2 B 13.10.2 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. 126 GS2200-8/24 User's Guide

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Chapter 13 Spanning Tree Protocol
GS2200-8/24 User’s Guide
126
13.10.1
MSTP Network Example
The following figure shows a network example where two VLANs are configured on the two
switches. If the switches are using STP or RSTP, the link for VLAN 2 will be blocked as STP and RSTP
allow only one link in the network and block the redundant link.
Figure 78
STP/RSTP Network Example
With MSTP, VLANs 1 and 2 are mapped to different spanning trees in the network. Thus traffic from
the two VLANs travel on different paths. The following figure shows the network example using
MSTP.
Figure 79
MSTP Network Example
13.10.2
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.
A
B
VLAN 1
VLAN 2
A
B
VLAN 1
VLAN 2