2Step 1 Ensure that all VLANs exist on the switches.Also,make sure that the ports have been configured in correct VLANs based on the topology diagram.
Step2 將 SW2 調整成為 vlan 10,11,20,22 的 Route Bridge，SW2 若掛掉由 SW1 取代，SW3 為 vlan 30 的 Route Bridge。
Step3 Enable PortFast and BPDU guard on the access ports on the three switches.
SW1#sh vlan
VLAN Name Status Ports
---- -------------------------------- --------- --------------------
1 default active Et0/1, Et0/2, Et0/3, Et1/3
10 VLAN0010 active Et0/0
11 VLAN0011 active Et0/0
20 VLAN0020 active
33 VLAN0033 active .....>設錯，少了22、30，多33
...
Step3 Enable PortFast and BPDU guard on the access ports on the three switches.
SW1#sh vlan
VLAN Name Status Ports
---- -------------------------------- --------- --------------------
1 default active Et0/1, Et0/2, Et0/3, Et1/3
10 VLAN0010 active Et0/0
11 VLAN0011 active Et0/0
20 VLAN0020 active
33 VLAN0033 active .....>設錯，少了22、30，多33
...
