Specifications

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DCS-3950 series Ethernet switch manual
By default, the MSTP establishes a tree topology (in blue lines) rooted with SwitchA.
The ports marked with ‘x’ are in the discarding status, and the other ports are in the
forwarding status.
Configurations Steps:
Step 1: Configure port to VLAN mapping:
z Create VLAN 20, 30, 40, 50 in SW2, SW3 and SW4.
z Set ports 1-7 as trunk ports in SW2, SW3 and SW4.
Step 2: Set SW2, SW3 and SW4 in the same MSTP:
z Set SW2, SW3 and SW4 to have the same region name as mstp.
z Map VLAN 20 and VLAN 30 in SW2, SW3 and SW4 to Instance 3; Map VLAN 40
and VLAN 50 in SW2, SW3 and SwitchD to Instance 4.
Step 3: Set SW3 as the root bridge of Instance 3; Set SW4 as the root bridge of Instance 4
z Set the bridge priority of Instance 3 in SW3 as 0.
z Set the bridge priority of Instance 4 in SW4 as 0.
The detailed configuration is listed below:
On SW2:
SW2(Config)#vlan 20
SW2(Config-Vlan20)#exit
SW2(Config)#vlan 30
SW2(Config-Vlan30)#exit
SW2(Config)#vlan 40
SW2(Config-Vlan40)#exit
SW2(Config)#vlan 50
SW2(Config-Vlan50)#exit
SW2(Config)#spanning-tree mst configuration
SW2(Config-Mstp-Region)#name mstp
SW2(Config-Mstp-Region)#instance 3 vlan 20;30
SW2(Config-Mstp-Region)#instance 4 vlan 40;50
SW2(Config-Mstp-Region)#exit
SW2(Config)#interface e 0/0/1-7
SW2(Config-Port-Range)#switchport mode trunk
SW2(Config-Port-Range)#exit
SW2(Config)#spanning-tree
On SW3:
SW3(Config)#vlan 20
SW3(Config-Vlan20)#exit
SW3(Config)#vlan 30
SW3(Config-Vlan30)#exit