My-Technet

First we configure configure U Turn-Hairpinning

global (inside) 1 interface

static (inside,inside) 192.168.1.0 192.168.1.0 netmask 255.255.255.255

Then the Backup route configuration

global (outside) 1 interface
nat (inside) 1 172.16.1.0 255.255.255.0
route inside 192.168.1.0 255.255.255.0 192.168.2.1 1 track 1 route outside 0.0.0.0 0.0.0.0 123.123.123.123 (External IP) track 2

sla monitor 123
type echo protocol ipIcmpEcho 192.168.2.1  interface inside num-packets 3 frequency 5 sla monitor schedule 123 life forever start-time now sla monitor

124 type echo protocol ipIcmpEcho 123.123.123.123 (External IP) interface outside num-packets 3 frequency 5 sla monitor schedule 124 life forever start-time now track 1

rtr 123 reachability track 2 rtr 124 reachability