Answer:
You can setup firewall rules with for example iptables on Linux. The rules should block source addresses of private IP ranges such as 192.168.*.* and 10.*. *. * etc. Check private IP ranges for full list.
It will however not guarantee prevention of IP spoofing in general as its not possible to prevent such attacks. Its the responsibility of ISPs. But the question asked for private IP spoofing and then the above works.