2018-8-15

Spanning-Tree

CAMPUS NETWORK 交换网

校园网的四个部分：

核心网络
数据中心
BRANCH 分支机构
TELEWORKER 远程拨号

多层交换机：具有数据包转发功能或具有路由功能的交换机

LOW LATENCY HIGH SPEED SCALABILITY

交换网三层

接入：ACCESS：Workgroup access

汇聚：DITRIBUTION：Policy-Based Connectivity

核心：CORE:high-speed switching

802.1q

生成树的作用：在冗余线路上防环

Spanning-tree的端口状态

Bloacking：max age=20s 到LISTENING 状态，当网络中所指定端口于根端口选出后将BLOCKING STATE 转为LISTENING STATE,最大20s

Listening

Learning forward delay=15s转发延时

Forwarding

交换机中对比MAC地址（桥）BRIDGE-ID 优先级+MAC地址

选出根后决定spanning-tree cost

802.1w

生成树种类：

Rapid spanning tree protocol（RSTP）基于IEEE 802.1W

三个状态，端口切换速度快，（CST通常5个过程，RSTP3个过程）

CST common spanning tree ===IEEE 802.1D

所有的控制数据流量都在本帧VLAN中传输

MST：multiple spanning tree protocol

一个生成树对多个VLAN，吧逻辑架构相似的VLAN放到一个生成树实例下，多个架构相似的VLAN拥有同样的生成树

一个生成树===多个VLAN

Per-VLAN spanning tree=PVST+ === per-vlan 802.1D

相较于普通的RSTP CST来说，无论有多少的VLAN生成树的结构都不改变，根桥永远都是固定的一台设备

PSVT+

对于每一个VLAN（一个VLAN既一个独立的逻辑架构）都有自己的生成树结构。此时SW1可以为VLAN10的根桥，SW2可以为VLAN20的根桥，基于VLAN独立的生成树结构

RAPID PVST+ ===PER-VLAN IEEE 802.1w（思科默认）

PVST+的升级版，将快速收敛的特性加入到了PVST+中

SW3#show spanning-tree
VLAN0001
Spanning tree enabled protocol ieee
Root ID Priority 32769
Address 0001.63CB.9E21
Cost 19
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 0090.2BC0.094C
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 20

Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/1 Altn BLK 19 128.1 P2p
Fa0/3 Desg FWD 19 128.3 P2p
Fa0/2 Root FWD 19 128.2 P2p
Fa0/4 Desg FWD 19 128.4 P2p

BRIDGE ID最小的作为根桥

优先级+VLAN-ID都相同的情况下，选择MAC地址最小的设备作为某个VLAN的根桥

SW3(config-if)#do show sp
VLAN0001
  Spanning tree enabled protocol ieee
  Root ID    Priority    32769
             Address     0001.63CB.9E21
             Cost        19
             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     0090.2BC0.094C
             Hello Time  2 sec  Max Age 20 sec  Forward Delay 15 sec
             Aging Time  20

Interface        Role Sts Cost      Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/1            Altn BLK 19        128.1    P2p
Fa0/3            Desg FWD 19        128.3    P2p
Fa0/2            Root FWD 19        128.2    P2p
Fa0/4            Desg FWD 19        128.4    P2p

VLAN0010
  Spanning tree enabled protocol ieee
  Root ID    Priority    32778
             Address     0090.2BC0.094C
             This bridge is the root
             Hello Time  2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    32778  (priority 32768 sys-id-ext 10)
             Address     0090.2BC0.094C
             Hello Time  2 sec  Max Age 20 sec  Forward Delay 15 sec
             Aging Time  20

Interface        Role Sts Cost      Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/1            Desg FWD 19        128.1    P2p
Fa0/2            Desg FWD 19        128.2    P2p

VLAN0020
  Spanning tree enabled protocol ieee
  Root ID    Priority    32788
             Address     0090.2BC0.094C
             This bridge is the root
             Hello Time  2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    32788  (priority 32768 sys-id-ext 20)
             Address     0090.2BC0.094C
             Hello Time  2 sec  Max Age 20 sec  Forward Delay 15 sec
             Aging Time  20

Interface        Role Sts Cost      Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/1            Desg LRN 19        128.1    P2p
Fa0/2            Desg LRN 19        128.2    P2p

VLAN0030
  Spanning tree enabled protocol ieee
  Root ID    Priority    32798
             Address     0090.2BC0.094C
             This bridge is the root
             Hello Time  2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    32798  (priority 32768 sys-id-ext 30)
             Address     0090.2BC0.094C
             Hello Time  2 sec  Max Age 20 sec  Forward Delay 15 sec
             Aging Time  20

Interface        Role Sts Cost      Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/1            Desg LRN 19        128.1    P2p
Fa0/2            Desg LRN 19        128.2    P2p

VLAN0040
  Spanning tree enabled protocol ieee
  Root ID    Priority    32808
             Address     0090.2BC0.094C
             This bridge is the root
             Hello Time  2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    32808  (priority 32768 sys-id-ext 40)
             Address     0090.2BC0.094C
             Hello Time  2 sec  Max Age 20 sec  Forward Delay 15 sec
             Aging Time  20

Interface        Role Sts Cost      Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/1            Desg LSN 19        128.1    P2p
Fa0/2            Desg LSN 19        128.2    P2p

桥ID必须为4096倍数

SW3(config)#spanning-tree vlan 10 priority ?
  <0-61440>  bridge priority in increments of 4096

VLAN 20优先级设为最高

SW3(config)#spanning-tree vlan 20 root primary 
SW1(config)#spanning-tree vlan 20 root secondary

非根桥选择一个根端口

接收根桥发送的BPDU

管理/控制平面流量

距离根桥COST值最小（接口带宽越大，则COST越小）
比较上游转发BPDU的交换机的桥ID，原则小。
比较端口ID（prot-ID）

Switch(config-if)#spanning-tree vlan 10 port-priority 
  <0-61440>  bridge priority in increments of 4096

Prot-ID=接口优先级+端口号

默认优先级为128

选择对端笑的PROT-ID的接口为根端口

指定端口：每条连接交换机的物理线路上的两个端口之一，必有一个指定端口转发/发送BPDU

根桥的所有端口都是指定端口需要发送BPDU
比较到达根桥的COST值，越小越优先
COST值相同，比较接口所在网桥的桥ID，越小越优先

MST配置

SW1(config)#spanning-tree mode mst
SW1(config)#spanning-tree mst configuration   //配置MST
SW1(config)#name CCIE
SW1(config)#revision 1
SW1(config)#instance 1 vlan 10，20

SW1(config)#spanning-tree mst 1 root primary  //1为主根
SW1(config)#spanning-tree mst 2 root secondary

CCNP-Spanning-Tree