User's Manual

17-11
After the above configuration, Switch1 is the root bridge of the instance 0 of the entire network. In the MSTP
region which Switch2, Switch3 and Switch4 belong to, Switch2 is the region root of the instance 0, Switch3 is
the region root of the instance 3 and Switch4 is the region root of the instance 4. The traffic of VLAN 20 and
VLAN 30 is sent through the topology of the instance 3. The traffic of VLAN 40 and VLAN 50 is sent through
the topology of the instance 4. And the traffic of other VLANs is sent through the topology of the instance 0.
The port 1 in Switch2 is the master port of the instance 3 and the instance 4.
The MSTP calculation generates 3 topologies: the instance 0, the instance 3 and the instance 4 (marked with
blue lines). The ports with the mark “x” are in the status of discarding. The other ports are the status of
forwarding. Because the instance 3 and the instance 4 are only valid in the MSTP region, the following figure
only shows the topology of the MSTP region.
Figure 17-3 The Topology Of the Instance 0 after the MSTP Calculation
Figure 17-4 The Topology Of the Instance 3 after the MSTP Calculation
Switch2
Switch3
Switch4
2 2
3 3X
4
4X
5
5X
6
7
6
7X
Switch1
Switch2
Switch3
Switch4
1
1 1X
2
2 2
3X 3
4
4
5
5X
6
7
6X
7X