Unicast RPF Examples

Unicast RPF is an input function and is applied on the interface of a router only in the ingress direction. 

Strict Mode RPF

If the source address is in the FIB and reachable only through the interface on which the packet was received, the packet is passed. The syntax for this method is ip verify unicast source reachable-via rx.  

Ref: http://www.cisco.com/en/US/docs/ios/12_3/security/command/reference/sec_i2g.html

http://www.cisco.com/web/about/security/intelligence/unicast-rpf.html