1、交换机二层增强特性实验记录一、 UDLD增强特性设计UDLD(UniDirectional Link Detection)工作原理介绍: UDLD针对光纤链路故障,工作在物理层模式,如果监测到单向的光纤链路故障出,可通过erro-disable状态强行将发生故障的端口关闭,避免单向链路故障引起生成树无法正常运算从而引起通信问题。设计范围与原则: 所有交换机的光纤端口都启用UDLD特性。 UDLD协商模式为主动方式(aggressive )。 Access-SW的接入端口不做设定测试配置udld网络是否瞬间中断,插拔单芯光纤观察端口状态(一) UDLD介绍 UDLD (UniDirectiona
2、l Link Detection 单向链路检测):是一个Cisco私有的二层协议,用于监听利用光纤或双绞线连接的以太链路的物理配置,当出现单向链路(只能向一个方向传输,比如我能把数据发给你,你也能收到,但是你发给我的数据我收不到)时,UDLD可以检测出这一状况,关闭相应接口并发送警告信息。单向链路可能引起很多问题,尤其是生成树,可能会造成回环。注意:UDLD需要链路两端设备都支持才能正常运行。 UDLD支持两种工作模式;普通(normal)模式(默认)和激进(aggressive)模式。 普通(normal)模式:这个模式下,UDLD可以检测单向链路,并标记端口为undetermined状态产
3、生系统日志,但并不影响流量转发。 激进(aggressive)模式:这个模式下,UDLD可以检测到由单向链路。并且会尝试重建链路,连续发送8秒的UDLD message,如果此间没有任何的UDLD echo应答,此端口会被放置于errdisable状态,并不允许任何流量通过。工作原理维护邻居数据库 UDLD周期型的在每个活动接口上发送hello包(也叫通告advertisement或探针probe)。 当交换机收到hello包后,存储这一信息直到老化时间到期,当老化时间到期前再次收到hello时,则刷新老化时间。检测和回报 交换机会向其邻居发送回复(echo),当邻居在一定时间内没有收到回复,
4、则认为与邻居间的链路出现问题。如果是普通模式,链路有可能会被认为是不确定的状态而不会被关闭(强调一下,普通模式只能检测光纤误解,比如Tx、Rx插反了)。如果是激进模式,则链路会被认为是单向的而被关闭(接口置于err-disable状态)。(二) Cisco下UDLD命令Cisco全局配置模式下:udld ? aggressive Enable UDLD protocol in aggressive mode on fiber ports except where locally configured enable Enable UDLD protocol on fiber ports exce
5、pt where locally configured message Set UDLD message parametersudld message ? time Set UDLD message time periodudld message time ? Time in seconds between sending of messages in steady stateCisco接口配置模式下:udld ? port Enable UDLD protocol on this interface despite global UDLD settingudld port ? aggress
6、ive Enable UDLD protocol in aggressive mode on this interface despite global UDLD setting disable Disable UDLD protocol on this interface despite global UDLD setting 关于errdisable恢复设置:errdisable recovery cause udlderrdisable recovery interval ? timer-interval(sec)注意:设备两端的光口,speed 需要设置成非自动协商,否则出现单向链路,
7、端口就会立即物理down,这是光口的特性,所以,如果光端口之间的speed能自动协商,是不需要udld这个功能的。(三) 使用单台Cisco3750进行环接测试1. 端口初始配置interface GigabitEthernet2/0/1 no switchport no ip address speed nonegotiate!interface GigabitEthernet2/0/2 speed nonegotiate spanning-tree portfast端口状态:Interface IP-Address OK? Method Status ProtocolGigabitEthe
8、rnet2/0/1 unassigned YES unset up up GigabitEthernet2/0/2 unassigned YES unset up up拔一芯,端口状态:Interface IP-Address OK? Method Status ProtocolGigabitEthernet2/0/1 unassigned YES unset up up GigabitEthernet2/0/2 unassigned YES unset down down一端端口依然up,另一端端口down,满足实验前提。2. 对端口设置udld,使用默认普通模式端口配置:interface
9、 GigabitEthernet2/0/1 no switchport no ip address speed nonegotiate udld port!interface GigabitEthernet2/0/2 speed nonegotiate udld port spanning-tree portfastshow udld:Interface Gi2/0/1-Port enable administrative configuration setting: EnabledPort enable operational state: EnabledCurrent bidirectio
10、nal state: BidirectionalCurrent operational state: Advertisement - Single neighbor detectedMessage interval: 7Time out interval: 5 Entry 1 - Expiration time: 45 Device ID: 1 Current neighbor state: Bidirectional Device name: FDO1515V0BS Port ID: Gi2/0/2 Neighbor echo 1 device: FDO1515V0BS Neighbor e
11、cho 1 port: Gi2/0/1 Message interval: 15 Time out interval: 5 CDP Device name: Switch Interface Gi2/0/2-Port enable administrative configuration setting: EnabledPort enable operational state: EnabledCurrent bidirectional state: BidirectionalCurrent operational state: Advertisement - Single neighbor
12、detectedMessage interval: 7Time out interval: 5 Entry 1 - Expiration time: 43 Device ID: 1 Current neighbor state: Bidirectional Device name: FDO1515V0BS Port ID: Gi2/0/1 Neighbor echo 1 device: FDO1515V0BS Neighbor echo 1 port: Gi2/0/2 Message interval: 15 Time out interval: 5 CDP Device name: Swit
13、ch 可见当期的邻居状态为Bidirectional,双向的。拔一芯,当Expiration time为0时,show udld:Interface Gi2/0/1-Port enable administrative configuration setting: EnabledPort enable operational state: EnabledCurrent bidirectional state: UnknownCurrent operational state: AdvertisementMessage interval: 7Time out interval: 5No neig
14、hbor cache information stored说是有log,目前没有产生log,这个需要研究下端口状态:GigabitEthernet2/0/1 unassigned YES unset up up GigabitEthernet2/0/2 unassigned YES unset down down3. 对端口设置udld,使用aggressive模式端口配置:interface GigabitEthernet2/0/1 no switchport no ip address speed nonegotiate udld port aggressive!interface Gig
15、abitEthernet2/0/2 speed nonegotiate udld port aggressive spanning-tree portfastshow udld:Interface Gi2/0/1-Port enable administrative configuration setting: Enabled / in aggressive modePort enable operational state: Enabled / in aggressive modeCurrent bidirectional state: BidirectionalCurrent operat
16、ional state: Advertisement - Single neighbor detectedMessage interval: 15Time out interval: 5 Entry 1 - Expiration time: 40 Device ID: 1 Current neighbor state: Bidirectional Device name: FDO1515V0BS Port ID: Gi2/0/2 Neighbor echo 1 device: FDO1515V0BS Neighbor echo 1 port: Gi2/0/1 Message interval:
17、 15 Time out interval: 5 CDP Device name: Switch Interface Gi2/0/2-Port enable administrative configuration setting: Enabled / in aggressive modePort enable operational state: Enabled / in aggressive modeCurrent bidirectional state: BidirectionalCurrent operational state: Advertisement - Single neig
18、hbor detectedMessage interval: 15Time out interval: 5 Entry 1 - Expiration time: 39 Device ID: 1 Current neighbor state: Bidirectional Device name: FDO1515V0BS Port ID: Gi2/0/1 Neighbor echo 1 device: FDO1515V0BS Neighbor echo 1 port: Gi2/0/2 Message interval: 15 Time out interval: 5 CDP Device name
19、: Switch拔一芯:当Expiration time为0时,show udldInterface Gi2/0/1-Port enable administrative configuration setting: Enabled / in aggressive modePort enable operational state: Enabled / in aggressive modeCurrent bidirectional state: UnknownCurrent operational state: Disabled portMessage interval: 7Time out
20、interval: 5No neighbor cache information stored有log输出:*Mar 1 17:08:54.088: %UDLD-4-UDLD_PORT_DISABLED: UDLD disabled interface Gi2/0/1, aggressive mode failure detected*Mar 1 17:08:54.088: %PM-4-ERR_DISABLE: udld error detected on Gi2/0/1, putting Gi2/0/1 in err-disable state*Mar 1 17:08:54.138: %LI
21、NEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet2/0/1, changed state to down*Mar 1 17:08:56.093: %LINK-3-UPDOWN: Interface GigabitEthernet2/0/1, changed state to down4. 一个端口设置udld aggressive,另一个端口不设置udld端口配置:interface GigabitEthernet2/0/1 no switchport no ip address speed nonegotiate udl
22、d port aggressive!interface GigabitEthernet2/0/2 speed nonegotiate spanning-tree portfastshow udld:Interface Gi2/0/1-Port enable administrative configuration setting: Enabled / in aggressive modePort enable operational state: Enabled / in aggressive modeCurrent bidirectional state: UnknownCurrent op
23、erational state: AdvertisementMessage interval: 7Time out interval: 5No neighbor cache information storedInterface Gi2/0/2-Port enable administrative configuration setting: Follows device defaultPort enable operational state: DisabledCurrent bidirectional state: Unknown可见,两个端口都没有学到邻居信息拔一芯,查看控制台,无输出,
24、可见,udld不起作用,因为学不到邻居信息所以,一对端口,必须同时启用udld,udld功能才能正常起作用。5. 一个端口udld设置默认模式,一个端口设置aggressive模式结果与udld定义一致,拔一芯,如果亮的端口设置的是默认模式,则一直亮;如果亮的端口设置的是aggressive模式,Expiration time为0,端口则会err-disabled。6. 关于errdisable recovery的测试配置如下:errdisable recovery cause udlderrdisable recovery interval 30拔一芯,log输出如下:*Mar 1 01:5
25、8:20.537: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet2/0/2, changed state to down*Mar 1 01:58:22.541: %LINK-3-UPDOWN: Interface GigabitEthernet2/0/2, changed state to down*Mar 1 01:59:05.055: %UDLD-4-UDLD_PORT_DISABLED: UDLD disabled interface Gi2/0/1, aggressive mode failure det
26、ected*Mar 1 01:59:05.055: %PM-4-ERR_DISABLE: udld error detected on Gi2/0/1, putting Gi2/0/1 in err-disable state*Mar 1 01:59:05.105: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet2/0/1, changed state to down*Mar 1 01:59:07.060: %LINK-3-UPDOWN: Interface GigabitEthernet2/0/1, change
27、d state to down*Mar 1 01:59:35.094: %PM-4-ERR_RECOVER: Attempting to recover from udld err-disable state on Gi2/0/1*Mar 1 01:59:37.166: %LINK-3-UPDOWN: Interface GigabitEthernet2/0/1, changed state to up*Mar 1 01:59:37.175: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet2/0/1, change
28、d state to upudld检测,发现端口出现单向链路,置端口err-disable状态,然后errdisable recovery起作用,端口状态被恢复成up,此时udld已经失效,因为依然是单向链路,学不到邻居信息。(四) 使用Cisco3750与LP连接测试与lp连接,3750g交换机端口speed不能设置nonegotiate,因为lp端口不亮,这样测试将无法进行。(五) 使用Cisco3750与H3C7506连接测试最后进行测试,需要16A插排,先往后进行。(六) 总结 UDLD,UniDirectional Link Detection单向链路检测,是Cisco私有的二层协议
29、,也是Cisco特有的名词。 当光纤链路,出现单向链路时,互联端口有时会出现一端端口亮up,一端端口灭down的情况,这种情况,会产生譬如生成树无法正常运算,影响通信,或者监控无法正常报警等问题,这时,如果光纤链路两端互联的设备均为Cisco,就可以通过udld这个特性解决此类问题。 这时,依然up的端口,如果配置成udld aggressive,则此端口会置为err-disable。 但是,如果光纤链路两端的端口speed是自动协商的,出现单向链路时,两端端口会都灭,是不需要udld的,这是光端口的特性。 所以,当光纤链路两端端口的speed协商模式是nonegotiate时,建议使用udl
30、d这个特性。配置示例:Switch(config)#errdisable recovery cause udldSwitch(config)#errdisable recovery interval 3600Switch(config)#int g2/0/1Switch(config-if)#udld port aggressive其中: errdisable recovery interval恢复时间为30到86400秒,默认为300秒,5分钟 当errdisable recovery后,如果依然是单向链路,则udld将失效,因为学不到对应的邻居信息,不能执行必要的hello检测,恢复的端口
31、,会一直up下去。注意: 光纤链路互联的两个端口,必须同时配置udld 如果光纤链路互联端口的speed可以自动协商,不需要使用udld,因为不会产生单向链路的问题,只要有一个链路有问题,互联两个端口都会down。二、 广播及组播流量控制设计Interface range fa0/1 -xxxstorm-control broadcast level 8.00 4.00storm-control multicast level 8.00 4.00storm-control action shutdown设计要点:ES交换机接入端口上监视广播及组播流量,通过控制广播及组播的流量实现对整体网络带宽的保护,在出现广播风暴时及时抑制。设定范围: 所有ES交换机接入端口。 通过对端口带宽广播及组播流量的百分比进行阀值设定。 LAN设定界限值(端