一、本文目的
静态路由+Track，实现路由的冗余切换
二、技术简介
静态路由：管理员手工填写，管理距离为1或0（静态路由下一跳为接口的情况下）
Track：追踪技术
IP SLA:IP 服务等级，通过该技术测试网络连通性
三、实验环境
模拟器：GNS3
路由器：unzip-c3725-adventerprisek9-mz.124-15.T5.bin
四、网络拓扑
五、环境要求
①.在路由器访问对端lo1接口默认走上面的链路，当上面的链路出问题时，切换到下面的链路
②.在路由器访问对端lo2接口默认走下面的链路，当下面的链路出问题时，切换到上面的链路
六、网络配置
R1：
track 1 rtr 1 reachability //跟踪路由可靠性
track 2 rtr 2 reachability
interface Loopback1
ip address 10.80.1.1 255.255.255.0
interface Loopback2
ip address 10.80.2.1 255.255.255.
interface FastEthernet0/0
ip address 172.20.0.17 255.255.255.252
interface FastEthernet0/1
ip address 172.20.0.29 255.255.255.252
ip route 10.70.1.0 255.255.255.0 172.20.0.18 track 1 //在此路由后面跟track，如果trackdown了，此路由失效，因为路由器会选择备份的路由
ip route 10.70.2.0 255.255.255.0 172.20.0.30 track 2
ip route 10.70.1.0 255.255.255.0 172.20.0.30 10 //配置管理距离为10，使该路由作为备份路由，当track的主路由失败后，则选择这个路由
ip route 10.70.2.0 255.255.255.0 172.20.0.18 10
ip sla 1 //配置SLA，根据icmp来判断链路是否可靠
icmp-echo 172.20.0.18 source-ip 172.20.0.17
ip sla schedule 1 life forever start-time now //配置schedule,是SLA立即生效，有效期为永远
ip sla 2
icmp-echo 172.20.0.30 source-interface FastEthernet0/1
ip sla schedule 2 life forever start-time now
R2：
track 1 rtr 1 reachability
track 2 rtr 2 reachability
interface Loopback1
ip address 10.70.1.1 255.255.255.0
interface Loopback2
ip address 10.70.2.1 255.255.255.0
interface FastEthernet0/0
ip address 172.20.0.18 255.255.255.252
interface FastEthernet0/1
ip address 172.20.0.30 255.255.255.252
ip route 10.80.1.0 255.255.255.0 172.20.0.17 track 1
ip route 10.80.2.0 255.255.255.0 172.20.0.29 track 2
ip route 10.80.1.0 255.255.255.0 172.20.0.29 10
ip route 10.80.2.0 255.255.255.0 172.20.0.17 10
ip sla 1
icmp-echo 172.20.0.17 source-ip 172.20.0.18
ip sla schedule 1 life forever start-time now
ip sla 2
icmp-echo 172.20.0.29 source-interface FastEthernet0/1
ip sla schedule 2 life forever start-time now
七、验证
R2#sho track brief
Track Object Parameter Value Last Change
1 rtr 1 reachability Up 00:00:37
2 rtr 2 reachability Up 01:10:57
R2#sho track
Track 1
Response Time Reporter 1 reachability
Reachability is Up
8 changes, last change 00:01:58
Latest operation return code: OK
Latest RTT (millisecs) 32
Tracked by:
STATIC-IP-ROUTING 0
Track 2
Response Time Reporter 2 reachability
Reachability is Up
8 changes, last change 01:12:18
Latest operation return code: OK
Latest RTT (millisecs) 20
Tracked by:
STATIC-IP-ROUTING 0
可以在R1在配置deny ACL测试（具体操作不在表述），测试结果如下：
本文参考文章：
http://www.firewall.cx/cisco-technical-knowledgebase/cisco-routers/813-cisco-router-ipsla-basic.html
