Static routing

[Saurabh Firke]

There are 2 paths from Site 1 to Site 2 means R1 to R3

R1 to R2 to R3 is primary link and
R1 to R4 to R5 is the secondary path.

Configure the static routing on all routers and

Fix the configuration so that when R1 transfer the data to R3, it uses the primary path r1 to r2 to r3

And if any case if this path went down then it uses a secondary path as R1 to R4 to R5

Verification:

Go to R1 router and
do Traceroute 3.3.3.3

it shows the path from
R1 to R2 to R3

Now go to the R2 router

and shutdown interface se1/1

#Interface se1/1
#Shutdown

==================================================================
Make note you need to down 145.18.18.12/29 interface on R2 router
==================================================================

After that come on the r1 router and do traceroute 3.3.3.3

Now replies

should go through R1 to R4 to R5 automatically.

Static Routing 

[MHM Cisco World]

it simple using IP SLA, 
check the below link it can help you

https://www.cisco.com/c/en/us/support/docs/ip/ip-routing/200785-ISP-Failover-with-default-routes-using-I.html

[Spooster IT Services]

Hi Saurbah ,  You can configure IP SLA  on router R1: 

1) Make a Tracking Object 

ip sla 100

icmp-echo 145.18.18.12 source-interface se1/1   

timeout 500        

frequency 3

(145.18.18.12 would be pinged through Serial1/1 every 3 seconds, and will timeout in 500 ms if a response is not received )

2) Create a Schedule for the Tracking Object

 ip sla schedule 100 life forever start-time now

(Tracking of145.18.18.12 would start immediately & stays on indefinitely )

3) Track the state of the Object 

track 100 rtr 100 reachability

 ( If there is no ping response to145.18.18.12 the track would go down & would only come up once it starts receiving the ping again ) 

4) Call the Track in the default route  

ip route 0.0.0.0 0.0.0.0 serial1/0 track 100

ip route 0.0.0.0 0.0.0.0 serial1/1 10

( Secondary path would only be used when the track goes down & the track would only go down if the router stops receiving the ping responses to the IP 145.18.18.12 which is being tracked )