4-STP增强特性：Backbonefast

一、实验拓扑：

二、实验要求：
1、SW1、SW2、SW3连接后，查看VLAN10的阻塞端口；
2、断开骨干链路后，查看阻塞端口NDP是否需要50s变为根端口RP，并进入：Fwarding状态？
3、在该交换机下部署Backbonefast命令，查看是否需要30s进入：Fwarding？

三、命令部署：
1、断开SW的f0/0端口：
SW3(config)#int f0/0
SW3(config-if)#shutdown

2、SW1、SW2、SW3全局模式下部署Backbonefast，目的让所有交换机出问题都可以快速加速：
SW1(config)#spanning-tree backbonefast
SW2(config)#spanning-tree backbonefast
SW3(config)#spanning-tree backbonefast

3、Debug
SW2#debug spanning-tree backbonefast
Spanning Tree backbonefast general debugging is on

四、验证：
1、断开SW3的f0/0端口，查看时间：分别经历了BLK、LIS、LRN、FWD共50S
SW2#show spanning-tree vlan 10 bri

Name Port ID Prio Cost Sts Cost Bridge ID Port ID

---

FastEthernet0/0 128.1 128 19 FWD 0 32768 cc14.a890.0001 128.2
FastEthernet0/1 128.2 128 19 BLK 19 32768 cc15.a890.0001 128.2

Name Port ID Prio Cost Sts Cost Bridge ID Port ID

---

FastEthernet0/0 128.1 128 19 FWD 0 32768 cc14.a890.0001 128.2
FastEthernet0/1 128.2 128 19 LIS 19 32768 cc16.a890.0001 128.2

Name Port ID Prio Cost Sts Cost Bridge ID Port ID

---

FastEthernet0/0 128.1 128 19 FWD 0 32768 cc14.a890.0001 128.2
FastEthernet0/1 128.2 128 19 LRN 19 32768 cc16.a890.0001 128.2

Name Port ID Prio Cost Sts Cost Bridge ID Port ID

---

FastEthernet0/0 128.1 128 19 FWD 0 32768 cc14.a890.0001 128.2
FastEthernet0/1 128.2 128 19 FWD 19 32768 cc16.a890.0001 128.2

2、SW1、SW2、SW3部署Backbonefast后，查看时间：分别经历了LIS、LRN、FWD共30S
SW2#show spanning-tree vlan 10 bri

Name Port ID Prio Cost Sts Cost Bridge ID Port ID

---

FastEthernet0/0 128.1 128 19 FWD 0 32768 cc14.a890.0001 128.2
FastEthernet0/1 128.2 128 19 LIS 19 32768 cc16.a890.0001 128.2

Name Port ID Prio Cost Sts Cost Bridge ID Port ID

---

FastEthernet0/0 128.1 128 19 FWD 0 32768 cc14.a890.0001 128.2
FastEthernet0/1 128.2 128 19 LRN 19 32768 cc16.a890.0001 128.2

Name Port ID Prio Cost Sts Cost Bridge ID Port ID

---

FastEthernet0/0 128.1 128 19 FWD 0 32768 cc14.a890.0001 128.2
FastEthernet0/1 128.2 128 19 FWD 19 32768 cc16.a890.0001 128.2