Implementing Spanning Tree Implementing MSTP

Multiple Spanning Tree Protocol CST和PVST都有不足之处，MSTP来补之；节省带宽，节省CPU；优化负载均衡。 Instance 1 maps to VLANs 1–500 Instance 2 maps to VLANs 501–1000

Extended System ID in Bridge ID Field

MST Regions MST configuration on each switch: Name Revision number 三个参数不同，不属于同一区域；关键是如何判断双方的VLAN映射相同（CST就是一个,PVST是每一个）；发送vlan-to-instance的mapping摘要。 MST configuration on each switch: Name Revision number VLAN association table

Interacting Between MST Regions and 802.1D

Configuring MSTP Enters MST configuration submode Switch(config)#spanning-tree mst configuration Enters MST configuration submode Switch(config-mst)#name name Sets the MST region name Switch(config-mst)#revision rev_num Sets the MST configuration revision number Switch(config-mst)#instance inst vlan range Maps the VLANs to an MST instance Switch(config)#spanning-tree mst instance_number root primary|secondary Establishes primary and secondary roots for MST instance

Verifying MSTP Displays MSTP configuration information Switch#show spanning-tree mst configuration Displays MSTP configuration information Switch#show spanning-tree mst configuration Name [cisco] Revision 1 Instance Vlans mapped -------- --------------------------------------------------------------------- 0 11-4094 1 1-10 -------------------------------------------------------------------------------

Verifying MSTP (Cont.) Switch#show spanning-tree mst instance_number Displays configuration information for a specific MSTP instance Switch#show spanning-tree mst 1 ###### MST01 vlans mapped: 1-10 Bridge address 00d0.00b8.1400 priority 32769 (32768 sysid 1) Root this switch for MST01 Interface Role Sts Cost Prio.Nbr Status ---------------- ---- --- --------- -------- -------------------------------- Fa4/4 Back BLK 1000 240.196 P2p Fa4/5 Desg FWD 200000 128.197 P2p Fa4/48 Boun FWD 200000 128.240 P2p Bound(STP) Switch#clear spanning-tree detected-protocols [interface interface-id] Forces renegotiation with neighboring switches during migration process

Summary MSTP reduces the encumbrance of PVST by allowing a single instance of spanning tree to run for multiple VLANs. An MST region is a group of MSTP switches that appears as a single virtual bridge to adjacent CST and MSTP regions. Extended system ID ensures that VLAN ID or MSTP instance can be carried in the Bridge ID field of a BPDU. An MSTP region requires an IST and an arbitrary number of MSTP instances as it connects to an 802.1Q network at the MST region border. MSTP is configured with a unique set of commands. MSTP implementation requires configuration and verification using specific configuration and show commands. MSTP减少PVST负担，通过允许一个单一实例的生成树来运行多个vlan。 一个MST区域是一组MSTP交换机,显示为单一虚拟桥相CST和MSTP地区。 扩展系统ID确保VLAN ID或MSTP实例可以通过这座桥的BPDU ID字段。 一个MSTP区域需要一个IST是和任意数量的MSTP实例作为它连接到一个802.1Q网络在MST区域边界。 MSTP配置了一套独特的命令。 MSTP实现需要配置和验证使用特定的配置和显示命令。