Figure 39 Stp/Rstp Network Example; Figure 40 Mstp Network Example - ZyXEL Communications ONU-2024 Series User Manual

Chapter 11 Spanning Tree Protocol
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 39 STP/RSTP Network Example

VLAN 1
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 40 MSTP Network Example

VLAN 1
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.
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A
VLAN 2
B
A
VLAN 2
B
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