IP SLA

1，拓扑图

2，

R1

ip sla 1  
 icmp-echo 12.1.1.2 source-ip 12.1.1.1
 frequency 5
ip sla schedule 1 life forever start-time now

track 8 ip sla 1 reachability

ip route 4.4.4.4 255.255.255.255 12.1.1.2 track 8
ip route 4.4.4.4 255.255.255.255 13.1.1.3 10