Unicast Reverse Path Forwarding (uRPF)
uRPF checks accessibility of source ip address. Actualy it designed to control for security to malicious traffic on L3 devivces (Router).
Generally it uses by isp and urpf prevents to create spoofed ip address by subscriber.
Router check source ip address which forward packet and does using FIB table performs. Whenever your router receives an IP packet it will check if it has a matching entry in the routing table for the source IP address
Urpf will do well if comes random fake source ip address from the back of the router. it helps to mitigation ddos attack
CEF must be open on Cisco Devices for URPF