使用以下命令依次判断：
Switch>en
Switch#show span
VLAN0001
Spanning tree enabled protocol ieee
Root ID Priority 32769
Address 0002.1617.5E91
Cost 38
Port 2(FastEthernet0/2)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32769 (priority 32768 sys-id-ext 1)
Address 0060.3E6A.95DD
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 20
Interface Role Sts Cost Prio.Nbr Type
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