Solution:
R1
Config t
Int et0/0
Ip flow monitor Monitor-R1Flow input
Ip flow monitor Monitor-R1Flow output
Exit
Ip sla 1
Icmp-echo 10.12.1.2
Freq 300
Ip sla schedule 1 life foreve start-time now
Sw1
Config t
Monitor session 12 source vlan 12
Monitor session 12 destination interface et1/3