参考stp生成树协议

STP的概念冗余拓扑Server/host

XRouter

YSegment

1Segment

2冗余拓扑能够解决单点故障问题；冗余拓扑造成广播风暴,多帧复用,MAC地址不稳定的问题；Switch

ASwitch

BSTP的概念广播风暴Host

X发送广播帧；交换机继续没完没了的更新广播流量；Server/host

XRouter

YSegment

1Segment

2Switch

ASwitch

BBroadcastSTP的概念多帧Server/host

XRouter

YSegment

1Segment

2Host

X发送一个单播数据帧给Router

Y；Router

Y的MAC地址还没有被每个交换机学习到；Router

Y接收2份相同的数据帧的拷贝；Switch

ASwitch

BunicastSTP的概念MAC表紊乱Server/host

XRouter

YSegment

1Segment

2Host

X发送一个单播数据帧给Router

Y；Router

Y的MAC地址还没有被每个交换机学习到；Switches

A

and

B在Port1上学习到Host

X的MAC地址；到达Router

Y的数据帧被泛洪；Switches

A

and

B不正确的在Port2上学习到Host

X的MAC地址；Switch

ASwitch

BunicastSTP的概念复杂的多环网络Server/hostWorkstationsLoopLoopLoopBroadcastSTP的概念采用生成树STP解决环路–

Spanning-Tree

Protocol通过将特定的端口选为Blocking

state，来实现无环的拓扑；IEEE

802.1D规定了这一行为；Cisco采用IEEE802.1D的增强的私有协议生成树PVST+;STP的操作每个广播域选择一个根桥每个非根桥上选择一个根端口每个段选择一个指定端口选择一个非指定端口10BASE-TSW1SW2SW3ROOT10BASE-TRoot

portDesignated

portDesignated

portRoot

port100BASE-TDesignated

portSTP的操作每个广播域选择一个根桥BPDU

(default

=

sent

every

2

seconds)Root

bridge

=

bridge

with

the

lowest

bridge

IDBridge

IDSwitch

YDefault

priority

32768(8000

hex)MAC

0c0022222222Switch

XDefault

priority

32768(8000

hex)MAC

0c0011111111BPDU桥优先级2字节6字节桥MAC地址STP的操作BPDUSTP的操作每个广播域选择一个根桥每个非根桥上选择一个根端口100BASE-T10BASE-T10BASE-TSW1SW2SW3ROOTDP

Designated

portRP

Root

port根端口：具有最低根路径的接口要考虑的因素：1最低的根桥ID2最低的根路径代价3最低发送者桥ID4

最

口IDSTP路径开销Link

SpeedCost

(New

IEEESpecification)Cost

(Old

IEEESpecification)10

Gb/s211

Gb/s41100

Mb/s191010

Mb/s100100最短路径是cost累加，而cost是基于链路的速率的。STP的操作每个广播域选择一个根桥每个非根桥上选择一个根端口100BASE-T10BASE-T10BASE-TSW1SW2SW3ROOTDP

Designated

portRP

RootportRPRP根端口：具有最低根路径的接口要考虑的因素：最低的根桥ID最低的根路径代价最低发送者桥ID最

口IDSTP的操作每个广播域选择一个根桥每个非根桥上选择一个根端口每个段选择一个指定端口100BASE-T10BASE-T10BASE-TSW1SW2SW3ROOTDP

Designated

portRP

RootportRPRPDPDP指定端口：具有最低根路径的接口要考虑的因素：最低的根桥ID最低的根路径代价最低发送者桥ID最

口IDSTP的操作每个广播域选择一个根桥每个非根桥上选择一个根端口每个段选择一个指定端口阻塞非指定端口100BASE-T10BASE-T10BASE-TSW1SW2SW3ROOTDP

Designated

portRP

RootportRPRPDPDPSTP案例CASE1SW1SW2SW3Pri

32768Mac

0C00.1111.0000ROOTDPPri

32768Mac

0C00.1111.1111Pri

32768Mac

0C00.1111.2222100

BASE-TRPRPSTP案例CASE2SW1SW2SW3ROOTDPPri

32768Mac

0C00.1111.1111Pri

32768Mac

0C00.1111.2222100

BASE-TRPRPPri

32768Mac

0C00.1111.0000DPDPSTP案例CASE3Pri

32768Mac

0C00.1111.0000ROOTSW1SW4SW2SW3Pri

32768Mac

0C00.1111.1111Pri

32768Mac

0C00.1111.3333RPRPPri

32768Mac

0C00.1111.2222RPDPDPDPDPSTP案例CASE4Pri

32768Mac

0C00.1111.0000ROOTSW1SW2Pri

32768Mac

0C00.1111.2222RPDPDPSTP的端口状态STP的端口状态In

the

blocking

state,

ports

can

only

receive

BPDUs.

It

may

take

up

to20

seconds

to

change

from

thisstate；In

listening

state,

switches

determine

if

there

are

any

other

paths

tothe

root

bridge.

the

forward

delay

and

lasts

for

15

seconds.

In

thelistening

state,

user

data

is

not

being

forwarded

and

MAC

addressesare

not

being

learned；In

learning

state

user

data

is

not

forwarded,

but

MAC

addresses

arelearned

from

any

traffic

that

is

seen.

The

learning

sta asts

for

15seconds

and

isalso

called

theforward

delay；In