STP RSTP MSTP PVST+学习 (2)

MAC media access control

STA spanning-tree Algorithm

hello time 2 second

01-80-c2-00-00-00

TCN  topoolgy change notification

 

DLC--------DLC Header-----------

 

DLC:

DLC: Frame 15 arrived at 11:02:20:8523:frame size is 60(003c)bytes.

DLC: Destination=Mulitcast 0180c2000000, Bridge_Group_Addr      2层多播地址

DLC: Source=station cisco 7A009A6   发送端口MAC地址

DLC: 802.3length = 39               长度

DLC

 

LLC:---------LLC Header------------

 

LLC:

LLC: DSAP Address = 42, DSAP IG Bit=00 (individual address)    0x42 代表 BPDU

LLC: SSAP Address = 42, SSAP CR Bit= 00 (command)        0x42 代表 BPDU

LLC: unnumbered frame:UI

LLC:

 

BPDU:-------Bridge Protocol Data Unit Header-------------

BPDU:Protocol identifier  = 0000                 0   协议ID

BPDU:Protocol Version = 00                        0   STP 为0   RSTP 2

BPDU:

BPDU: BPDU Type = 00 (configuration)   00 配置BPDU  80 TCN BPDU

BPDU:

BPDU:BPDU Flags = 00  LSB = TC 标记  MSB=TCN 标记

BPDU:0... .... = Not Topology Change Acknowledgement

BPDU:.... ...0 = Not Topology Change

BPDU:000 000. = Unused

BPDU:

BPDU:Root identifier= 8000.004000BA009A2      根网桥ID

BPDU:Priority = 8000                                              优先级

BPDU:MAC Address = 00400BA009A2                MAC地址

BPDU:

BPDU:Root Path Cost = 0                                        根路径成本

BPDU:Sending Bridge id = 8000.00400BA009A2.8005    发送网桥ID

BPDU:Priority = 8000                                              发送网桥优先级

BPDU:MAC Address = 0040BA009A2                   发送网桥MAC

BPDU:Port = 8005                                                     端口ID

BPDU:Message Age =0.000 seconds                         自根发出BPDU之后的时间

BPDU:Information Lifetime = 20.000 seconds         

BPDU:Root Hello Time = 20.000 seconds

BPDU:Forwarding Delay = 15.000 seconds

BPDU:

 

DLC: Frame Padding =7 btyes                                    填充

 

LSB  least significant bit  最低有效位

MSB most significant bit  最高有效位

RP   root port

DP  designated  port

N-DP  nondesignated port

hello 时间默认为2秒 配置为1-10秒之间的某个数值

forwarding delay  默认为15秒 可以配置为 4-30秒

当网络拓朴处于过渡期的时候，将不传递任何用户数据

 

 

 

MAC地址分配和缩减

 

Catalyst 交换机MAC地址池最多可以支持1024个MAC地址

交换机型号决定了可用MAC地址的数目，并不是所有交换机都支持1024个MAC地址

最后一个MAC地址分配给supervisor engine 的带内管理接口 sc0

如果交换机所拥有的MAC地址数目少于所支持的VLAN数目，那么MAC地址缩减就支持4094个STP实例。

 

系统ID扩展 system id extension

 

|------------------------16bit-----------------|------------------------48bit---------------------------------|

|                 优先级                                   |                             MAC地址                                    |

 

|----4bit------|---------- 12bit----------------|-----------------------48bit---------------------------------|

  优先级               系统ID扩展                                            MAC地址

 

如果启用MAC地址缩减特性， 网桥优先级就成为了4096的倍数加上VLAN ID。

 

0 4096  8192   12288  16384  20480  24576  28672   32768  36864  40960  45056  49152   53248

57344  61440

 

catalyst 交换机上STP 默认模式是 PVST+，PVST+ 模式为每一个VLAN 运行一个STP实例

 

switch# conf t

switch(config)# spanning-tree vlan 100

switch(config)# spanning-tree vlan 100 priortiy 4096

switch(config)# spanning-tree vlan 100 root primary

switch(config)# spanning-tree vlan 100 root secondary

 

 

我们建议给跟网桥指定的根优先级值是 4096

通过手工配置优先级，可以为根网桥和辅助跟网桥获得确定性的优先级数值。是推荐的做法

接口介质决定了生成树端口路径开销的默认值

 

 

switch(config)# interface fastethernet 1/4

switch(config-if)# spanning-tree cost 10

switch(config)#interface fastethernet 1/5

switch(config-if)# switchport trunk encapsulation dot1q

switch(config-if)#switchport mode trunk

swtich(config-if)# spanning-tree vlan 10 cost 20

 

2950# show spanning-tree vlan 68

Spanning tree 68 is executing the IEEE compatible Spanning Tree protocol
  Bridge Identifier has priority 32768, address 0007.eb7c.4a84
  Configured hello time 2, max age 20, forward delay 15
  We are the root of the spanning tree
  Topology change flag not set, detected flag not set, changes 7
  Times:  hold 1, topology change 35, notification 2
          hello 2, max age 20, forward delay 15
  Timers: hello 0, topology change 0, notification 0

Interface Fa0/1 (port 7) in Spanning tree 68 is down
   Port path cost 100, Port priority 128
   Designated root has priority 32768, address 0007.eb7c.4a84
   Designated bridge has priority 32768, address 0007.eb7c.4a84
   Designated port is 7, path cost 0
   Timers: message age 0, forward delay 0, hold 0
   BPDU: sent 0, received 0

Interface Fa0/7 (port 13) in Spanning tree 68 is FORWARDING
   Port path cost 19, Port priority 128
   Designated root has priority 32768, address 0007.eb7c.4a84
   Designated bridge has priority 32768, address 0007.eb7c.4a84
   Designated port is 13, path cost 0
   Timers: message age 0, forward delay 0, hold 0
   BPDU: sent 274349, received 0

Interface Fa0/23 (port 29) in Spanning tree 68 is FORWARDING
   Port path cost 19, Port priority 128
   Designated root has priority 32768, address 0007.eb7c.4a84
   Designated bridge has priority 32768, address 0007.eb7c.4a84
   Designated port is 29, path cost 0
   Timers: message age 0, forward delay 0, hold 0
   BPDU: sent 274360, received 0

 

2950#show spanning-tree brief

 

VLAN68
  Spanning tree enabled protocol IEEE
  ROOT ID    Priority 32768
             Address 0007.eb7c.4a84
             This bridge is the root
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    32768
             Address     0007.eb7c.4a84
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec
         

Port                           Designated
Name    Port ID Prio Cost Sts  Cost  Bridge ID      Port ID
------- ------- ---- ---- ---  ----  -------------- -------
Fa0/1   128.7   128  100  BLK  0     0007.eb7c.4a84 128.7 
Fa0/7   128.13  128  19   FWD  0     0007.eb7c.4a84 128.13
Fa0/23  128.29  128  19   FWD  0     0007.eb7c.4a84 128.29

 

2950#   show spanning-tree vlan 68 interface fastEthernet 0/7

 

Spanning tree 68 is executing the IEEE compatible Spanning Tree protocol
  Bridge Identifier has priority 32768, address 0007.eb7c.4a84
  Configured hello time 2, max age 20, forward delay 15
  We are the root of the spanning tree
  Topology change flag not set, detected flag not set, changes 7
  Times:  hold 1, topology change 35, notification 2
          hello 2, max age 20, forward delay 15
  Timers: hello 0, topology change 0, notification 0

Interface Fa0/7 (port 13) in Spanning tree 68 is FORWARDING
   Port path cost 19, Port priority 128
   Designated root has priority 32768, address 0007.eb7c.4a84
   Designated bridge has priority 32768, address 0007.eb7c.4a84
   Designated port is 13, path cost 0
   Timers: message age 0, forward delay 0, hold 0
   BPDU: sent 274711, received 0

 

show spanning-tree [bridge-group| active | backbonfast| {bridge [ id ]} | detail | inconsistentports |

{interface interface-type number} | root | summary [total] | uplinkfast | {vlan vlan-id}| port-channel

number} | pathcost method]

 

Changeing the Spanning-Tree Mode

 

switch# configure termianl

switch(config)#spanning-tree mode pvst

switch(config)#spanning-tree mode mst

switch(config)#spanning-tree mode rapid-pvst

 

pvst to enable pvst+ (the default setting)

mst to enable MSTP (and RSTP)

rapid-pvst to enable rapid PVST+

 

switch#show spanning-tree summary

switch#show spanning-tree interface interface-id

 

switch(config)#no spanning-tree vlan vlan_id

switch#show spanning-tree detail

 

switch(config)#spanning-tree vlan vlan_id root primary [diameter net-diameter[hello-time seconds]

 

For diameter net-diameter, specify the maximum number of switches between any two end stations.The range is 2 to 7.

For hello-time seconds,specify the interval in seconds  between the generation of configuration messages by the root switch.The range is 1 to 10; the default is 2.

 

switch(config)#spanning-tree vlan vlan-id root secondary [diameter net-diameter [hello-time seconds]]

 

 

switch(config)#interface interface-id

switch(config-if)#spanning-tree port-priority priority

switch(config-if)#spanning-tree vlan vlan_id port-priority priority

switch#show spanning-tree interface interface-id

switch#show spanning-tree vlan vlan_id

 

switch(config)#spanning-tree vlan vlan_id hello-time seconds

switch(config)#spanning-tree vlan vlan_id forward-time seconds

switch(config)#spanning-tree vlan vlan_id max-age seconds

switch(config)#spanning-tree vlan vlan_id hold-count value

 

switch#show spanning-tree active

displays spanning-tree information on active interface only.

 

switch#show spanning-tree detail

displays a detailed summary of interface information

 

switch#show spanning-tree interface interface-id

 

switch#show spanning-tree summary [total]