Building Redundant Switched Topologies

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
...

Configure Root Bridge and Analyze STP Topology

2p64.  Step 1~ step 8
SW1#sh spanning-tree vlan 20
VLAN0020
  Spanning tree enabled protocol ieee
  Root ID    Priority    32788
             Address     aabb.cc00.0100
             This bridge is the root (因為 SW1 MAC Addr 最小)
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    32788  (priority 32768 sys-id-ext 20)
             Address     aabb.cc00.0100
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec
             Aging Time  300 sec
Interface           Role Sts Cost      Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Et0/1               Desg FWD 100       128.2    Shr
Et0/2               Desg FWD 100       128.3    Shr