interface Ethernet0/0
nameif primary
security-level 0
ip address 172.16.10.1 255.255.255.0
!
interface Ethernet0/1
nameif backup
security-level 0
ip address 172.16.20.1 255.255.255.0
!
!
route primary  0.0.0.0 0.0.0.0 172.16.10.10 1
route backup   0.0.0.0 0.0.0.0 172.16.20.10 254
!
sla monitor 123
type echo protocol ipIcmpEcho 10.0.0.1 interface outside
num-packets 3
frequency 10
!
sla monitor schedule 123 life forever start-time now
!
track 1 rtr 123 reachability