3ComCISCO交换机实现链路容错Word下载.docx
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Maxage(最大等待时间)
NumberofsecondsaswitchwaitswithoutreceivingSTPconfigurationmessagesbeforeattemptingareconfiguration.Thisparametertakeseffectwhenaswitchisoperatingastherootswitch.Switchesnotactingastherootusetheroot-switchMaxageparameter.
Enteranumberfrom6to200.
HelloTime(轮询间隔时间)
Numberofsecondsbetweenthetransmissionofhellomessages,whichindicatethattheswitchisactive.Switchesnotactingasarootswitchusetheroot-switchHello-timevalue.
Enteranumberfrom1to10.
ForwardDelay(转发延迟时间)
NumberofsecondsaportwaitsbeforechangingfromitsSTPlearningandlisteningstatestotheforwardingstate.Thiswaitisnecessarysothatotherswitchesonthenetworkensurenoloopisformedbeforetheyallowtheporttoforwardpackets.
Enteranumberfrom4to200.
只要简单地减少“MaxAge”和“ForwardDelay”的时间,就能显著降低Spanning-tree的收敛时间。
在实际测试中,我们设置MaxAge=6,ForwardDelay=4,就能使3COMSSII1100交换机的冗余链路切换时间由原来的50s降低到6~10秒。
试验中,我们用2台CiscoCatalyst3524作为核心交换机,其中3524A被配置成Spanning-treed根(root);
用1台3ComSuperStackII1100交换机模拟第二级交换机,从SSII1100的25、26端口分别上连到3524A和3524B;
连接两台工作站(Windows98)到3524A和SSII1100上,互相Ping对方。
3524A(config)#spanning-treemax-age6
3524A(config)#spanning-treeforward-time4
3524A#shspanning-tree
Spanningtree1isexecutingtheIEEEcompatibleSpanningTreeprotocol
BridgeIdentifierhaspriority1,address0001.9660.7640
Configuredhellotime2,maxage6,forwarddelay4
Wearetherootofthespanningtree
Topologychangeflagnotset,detectedflagnotset,changes68
Times:
hold1,topologychange10,notification2
hello2,maxage6,forwarddelay4
Timers:
hello1,topologychange0,notification0
3524A的配置文件
version12.0
noservicepad
servicetimestampsdebuguptime
servicetimestampsloguptime
noservicepassword-encryption
!
hostname3524A
enablesecret5$1$Bvzy$z0vyaHlsK2nQkujvSawqq/
spanning-treevlan1priority1
spanning-treevlan1max-age6
spanning-treevlan1forward-time4
ipsubnet-zero
interfaceFastEthernet0/1
spanning-treeportfast
interfaceFastEthernet0/2
interfaceFastEthernet0/3
……
interfaceFastEthernet0/23
interfaceFastEthernet0/24
interfaceGigabitEthernet0/1
interfaceGigabitEthernet0/2
interfaceVLAN1
ipaddress192.168.1.10255.255.255.0
noipdirected-broadcast
noiproute-cache
snmp-serverengineIDlocal000000090200000196607640
snmp-servercommunityprivateRW
snmp-servercommunitypublicRO
snmp-serverchassis-id0x12
linecon0
transportinputnone
stopbits1
linevty04
password123
login
linevty515
end
3524B的配置文件
hostname3524B
enablesecret5$1$IqQ.$5IouBhKjqTplVd41AinGf.
spanning-treevlan1priority16384
portgroup1
ipaddress192.168.1.100255.255.255.0
snmp-serverengineIDlocal0000000902000001965DE100
exec-timeout00
3524B#shspanning-tree
BridgeIdentifierhaspriority8888,address0001.965d.e100
Configuredhellotime2,maxage20,forwarddelay15
Currentroothaspriority1,address0001.9660.7640
Rootportis1,costofrootpathis19
Topologychangeflagnotset,detectedflagnotset,changes65
hold1,topologychange21,notification2
hello0,topologychange0,notification0
方法二
与Cisco的Uplink-Fast技术相似,3COM也有独特的技术,用于缩短这种冗余上连链路的切换时间,名为“弹性链路”(ResilientLink)。
经过我们的测试,ResilientLink技术配置在第二级交换机上(SSII1100),并且可以独立地起作用。
但如果使用Cisco交换机作为核心层,必须同时按照方法1中的配置,调整Spanning-tree的参数,这样的配置能够达到最佳的结果,链路切换时间降低到4~6秒,并且使主链路的回切时间降低到零,即当主链路又恢复功能时,网络不会有任何中断,这点连Cisco的Uplink-Fast都不能做到。
试验中,3ComSuperStackII1100交换机的配置过程如下,2台Catalyst3524的配置同上。
Menuoptions:
---------3ComSuperStackIISwitch1100-----------
bridge-Administerbridging/VLANS
ethernet-AdministerEthernetports
feature-Administersystemfeatures
ip-AdministerIP
logout-LogoutoftheCommandLineInterface
snmp-AdministerSNMP
system-Administersystem-levelfunctions
Type?
forhelp.
----------------------------Switch1100
(1)--------------------
Selectmenuoption:
bridge
Selectmenuoption(bridge):
display
stpState:
enabledagingTime:
1800
Timesincetopologychange:
0hrs8mins17seconds
TopologyChanges:
1
BridgeIdentifier:
800000509980a3b8
DesignatedRoot:
0001000196607640
maxAge:
20bridgeMaxAge:
20
helloTime:
2bridgeHelloTime:
2
forwardDelay:
15bridgeFwdDelay:
15
holdTime:
1rootCost:
18
rootPort:
25priority:
0x8000
------------------------------Switch1100
(1)------------------
feature
analyzer-AdministerRovingAnalysis
broadcastStormCont-Enable/DisableBroadcastStormControl
resilience-Administerresilientlinks
trunk-Administertrunks
Type"
q"
toreturntothepreviousmenuor?
-------------------------------Switch1100
(1)------------------
Selectmenuoption(feature):
resilience
define-Definearesilientlink
detail-Displayresilientlinkinformation
remove-Removearesilientlink
swap-Swapoverresilientlinkports
Selectmenuoption(feature/resilience):
define
Selectunitformainlink
(1):
Selectportformainlink
(1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26):
25
Selectunitforstandbylink
(1):
Selectportforstandbylink
(1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,26):
26
detail
Resilientlinksummary
IndexMainLinkStateStandbyLinkStateActiveLinkPairState
1Unit1Port25ActiveUnit1Port26OkMainOperational
结论
但对于营业部来说,6秒的断线已经会造成无盘工作站的掉网,所以即时将3Com交换机的链路容错切换时间降低到最短,依然不如CiscoUplink-fast的效果。
在进行网络改造是,我们建议:
第一,淘汰3Com以太网Hub,因为它们不支持Spanning-tree,不能提供任何链路容错。
第二,将3Com局域网交换机部署在网络的第三层,而核心层和第二层均采用Cisco交换机,利用Uplink-fast构建高可靠性的骨干网。