SLA&EEM检测MSTP线路加快路由收敛

SLA&EEM检测MSTP线路加快路由收敛
SLA&EEM检测MSTP线路加快路由收敛 首先介绍下背景：客户单位的网点目前使用的线路是SDH+FR，网点到地市核心使用的路由协议为RIP，根据实际测试，出现链路故障时，不做任何优化的情况下路由收敛需要4分钟。客户单位有计划将网点的FR线路升级为MSTP。       众所周知，MSTP线路如果在中间某一点出现故障，是不会导致设备物理端口出现协议层down的。物理接口处于UP状态时，路由是不会进行收敛的。为了避免此种情况，并加快网络收敛速度，思科工程师建议使用IP SLA+EEM。于是使用两台Cisco2801进行模拟测试，使用的IOS为c2801-entbasek9-mz.150-1.M.bin。      模拟拓扑如下：      设备的主要配置如下：      R1: hostname R1 ! boot-start-marker boot-end-marker ! enable secret 5 $1$HYYK$evVsS7tjNc5JkX/VuIhCE0 ! no aaa new-model no network-clock-participate wic 1 dot11 syslog ip source-route ! ! !          ! ip cef no ip domain lookup multilink bundle-name authenticated ! ! ! ! ! archive log config   hidekeys ! ! controller E1 0/1/0 line-termination 75-ohm channel-group 0 unframed ! ! track 1 ip sla 1 ! ! !          ! interface Loopback0 ip address 56.16.0.1 255.255.255.0 ! interface Loopback1 ip address 56.16.128.1 255.255.255.0 ! interface FastEthernet0/0 ip address 56.16.234.1 255.255.255.252 speed 100 full-duplex ! interface FastEthernet0/1 speed 100 full-duplex ! interface Serial0/1/0:0 ip address 56.16.244.1 255.255.255.252 ! router rip version 2 offset-list 0 in 3 Serial0/1/0:0 offset-list 0 out 3 Serial0/1/0:0 network 56.0.0.0 no auto-summary ! ip forward-protocol nd ! ! ip http server no ip http secure-server ip route 56.16.234.2 255.255.255.255 FastEthernet0/0 ! ip sla 1 icmp-echo 56.16.234.2 frequency 5 ip sla schedule 1 life forever start-time now disable-eadi ! tftp-server flash:c2801-entbasek9-mz.150-1.M.bin !scheduler allocate 20000 1000 event manager environment 1 event manager applet rip_track_1 event track 1 state down action 1.0 cli command "enable" action 2.0 cli command "conf t" action 3.0 cli command "int f 0/0" action 3.1 cli command "shut"   //shut物理端口后，路由表就会发生变化，原本从F0/0学到的路由删除，取而代之的是从S0/1/0：0学到的路由 action 3.2 cli command "no sh" //执行no shut命令是为了避免MSTP链路恢复了，端口仍处于关闭状态。反正MSTP线路故障不恢复的话就算UP了，也收不到路由更新。 action 4.0 cli command "end" ! end R2： hostname R2 !! track 1 ip sla 1 ! ! ! !          interface Loopback0 ip address 56.26.0.1 255.255.255.0 ! interface Loopback1 ip address 56.26.128.1 255.255.255.0 ! interface FastEthernet0/0 ip address 56.16.234.2 255.255.255.252 speed 100 full-duplex ! interface FastEthernet0/1 speed 100 full-duplex ! interface Serial0/1/0:0 ip address 56.16.244.2 255.255.255.252 ! router rip version 2 offset-list 0 in 3 FastEthernet0/1 offset-list 0 out 3 FastEthernet0/1 network 56.0.0.0 no auto-summary ! ip forward-protocol nd ! ! ip http server no ip http secure-server ip route 56.16.234.1 255.255.255.255 FastEthernet0/0 ! ip sla 1 icmp-echo 56.16.234.1 frequency 5 ip sla schedule 1 life forever start-time now disable-eadischeduler allocate 20000 1000 event manager environment 1 event manager applet rip_track_2 event track 1 state down action 1.0 cli command "enable" action 2.0 cli command "conf t" action 3.0 cli command "int f 0/0" action 3.1 cli command "shut" action 3.2 cli command "no sh" action 4.0 cli command "end" ! end    当两个交换机之间的连线拔掉之后，track 1 可以发现56.16.234.2无法ping到，SLA状态转为down，触发了EEM，执行EEM定义的语句。 *Jan  9 05:58:40.911: %TRACKING-5-STATE: 1 ip sla 1 state Up->Down *Jan  9 05:58:40.995: %SYS-5-CONFIG_I: Configured from console by  on vty0 (EEM:rip_track_1) *Jan  9 05:58:42.963: %LINK-3-UPDOWN: Interface FastEthernet0/0, changed state to up 再查看路由表时，路由已经是从S0/1/0：0学习到的。在配置中的探测频率与延时情况下，粗略判断路由收敛的时间在5秒左右，比自行收敛快数十倍。 其中有一个需要注意到地方是配置中的那条主机路由：ip route 56.16.234.2 255.255.255.255 FastEthernet0/0 用于确保探测对端地址的ICMP报文只能从F0/0发出，避免ICMP探测报文从其他路径到达目标，造成误判

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