实现 生成树 实现 RSTP
快速生成树（Rapid Spanning Tree Protocol） RSTP收敛速度很快（比较802.1D和uplinkfast等）；端口的角色和端口的状态隔离；链路类型（全工，半工）；协商机制；拓扑变化；和802.1D兼容 （disabled，blocking，listening，learning，forwarding变成discarding，discarding，discarding，learning，forwarding）
RSTP 端口状态
RSTP 端口角色 RP—AP DP--BP
什么是边缘接口? Will never have a switch connected to it Immediately transitions to forwarding Functions similarly to PortFast Configured by issuing the spanning-tree portfast command
RSTP 链路类型 Slide 2 of 2 Emphasize: What will happen if switch X fails? Switch Y will detect the missing BPDU from switch X in 20 seconds (max. age timer), then recalculate the Spanning Tree Protocol. After the network converges, switch Y will be the root bridge, and all its ports will transit to the forwarding states (DP) 30 seconds after the max. age timer expires.
RSTP BPDU 标识位： 3次hello没受到立刻老化BPDU，发起协商,半双工发协商不会回复
RSTP 协商进程： 快速协商：EP和点到点的链路 同步：把所有非EP端口阻塞掉
RSTP 下游的协商： Root and switch A synchronize. Ports on A come out of sync. Proposal or agreement takes place between A and B.
RSTP 拓朴改变机制 只有down到up才会拓扑改变，只有非EP端口才会发生拓扑改变，RSTP会触发一个2次hello时间的计时器，情况相应接口的MAC清空
PVRST 实现命令 Configuring Verifying Debugging spanning-tree mode rapid-pvst Verifying show spanning-tree vlan 101 Debugging debug spanning-tree
怎么实现 Rapid PVRST
检查 PVRST Display spanning tree mode is set to PVRST. Switch# show spanning-tree vlan 30 VLAN0030 Spanning tree enabled protocol rstp Root ID Priority 24606 Address 00d0.047b.2800 This bridge is the root Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Bridge ID Priority 24606 (priority 24576 sys-id-ext 30) Aging Time 300 Interface Role Sts Cost Prio.Nbr Type -------- ----- --- --- -------- ---- Gi1/1 Desg FWD 4 128.1 P2p Gi1/2 Desg FWD 4 128.2 P2p Gi5/1 Desg FWD 4 128.257 P2p Display spanning tree mode is set to PVRST.
总结： RSTP provides faster convergence than 802.1D STP when topology changes occur. RSTP defines three port states: discarding, listening, and forwarding. RSTP defines five port roles: root, designated, alternate, backup, and disabled. Edge ports forward while topology changes occur. RSTP makes use of two link types–P2P and shared. 802.1w uses the BPDU differently from 802.1D. Convergence results from the proposal and agreement process conducted switch by switch. The RSTP topology change notification process differs from 802.1D. Various commands are used to configure and verify PVRST. PVRST enables RSTP while still maintaining PVST. RSTP提供更快的收敛比802.1 d STP当拓朴改变发生时。 RSTP定义了三个端口状态:丢弃、侦听和转发。 RSTP定义五个端口角色:根、指定、交替、备份和关闭。 边缘端口转发而拓扑发生改变。 RSTP利用两个链接类型p2p和共享。 802.1 w使用BPDU不同于802.1 d。 收敛的结果建议和协议过程进行了交换机和交换机。 RSTP拓扑更改通知的过程不同于802.1 d。 各种命令是用于配置和验证PVRST。