利用MST来实现VLAN间的负载均衡
Sw1
       En
       Conf t
       Host sw1
       Interface range f0/13-15
       Sw mo tr
       Exit
       Vtp domain vlan
       Vtp mode server
       Vtp password wjc
       Vtp prunning
       Spanning-tree mode mst
       Spanning-tree mst configuration
       Name vlan1-2
       Revision 10   [0-65535]
       name vlan3-4
       revision 20
       Instance 1 vlan 1
       Intstance 1 vlan 2
       Instance 3 vlan 3
       Instance 3 vlan 3
       Exit
       Spanning-tree mst root primary
       Spanning-tree mst root secondary
Sw2
       En
       Con t
       Host sw2
       Interface range f0/13-15
       Sw mo tr
       Exit
       Vtp domain vlan
       Vtp mode client
       Vtp password wjc
       Spanning-tree mode mst
       Spanning-tree mst configuration
       Name vlan3-4
       Revision 20
       Name vlan1-2
       Revision 10
       Instance 1 vlan 1
       Instance 1 vlan 2
       Instance 3 vlan 3
       Instance 4 vlan 4
       Exit
       Spanning-tree mst 3 root primary
       Spanning-tree mst 1 root secondary
Sw3
       En
       Conf t
       Hostname sw3
       Interface range f0/14-15
       Sw mo tr
       Exit
       Vtp domain vlan
       Vtp mode client
       Vtp password wjc
Sw4
       En
       Conf t
       Hostname sw3
       Interface range f0/14-15
       Sw mo tr
       Exit
       Vtp domain vlan
       Vtp mode client
       Vtp password wjc