Руководство По Проектированию для Cisco Cisco Nexus 5010 Switch
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Another switch connected to the region previously defined can be configured as follows:
spanning-tree mst configuration
name dc1
revision 1
instance 1 VLAN 1-500
instance 2 VLAN 501-1000
This configuration defines a different region than the one that had only one instance configured. The
communication between the two MST regions uses instance 0 and the ports interconnecting the two switches are
boundary ports.
Note: For switches to belong to different regions, it is enough that the revision number be different.
This particular aspect of MST may appear intimidating because it is possible to have different regions within the
same Layer 2 topology as the result of a change in the VLAN mapping in one of the switches. In reality, while
changing the VLAN mapping causes some minor disruption, the forwarding topology always converges to help
ensure connectivity between hosts, as Figure 2 illustrates.
Figure 2. In MST Different Region Mappings Define Different Regions
In Figure 2, Agg1 is configured with, for example, VLAN A, B, C, and D belonging to topology 1, and E, F, G, and H
mapped to instance 2 (topology 2). The forwarding topology of each instance is color coded in the figure: the
dashed line represents instance 1, and the dash-dot line represents instance 2.