Help with Unicast Reverse Packet Forwarding (uRFP)

[lbogiani]

I'm trying to implement some sort of anti spoofing measure on my router (Cisco 806 DSL router) and was reading about uRFP. From what i understand you can use this in place of applying ingress and egress ACLs on the interfaces connecting to external networks. I applied this on my dialer interface and after this I was unable to browse the web at all. I disabled uRFP and was back to normal.

I read uRFP can have problems with asymetrical routing and will discard packets incorrectly. From what i understand asymetrical routing is where the packet does not take the same path from A to B than from B to A, if this is the case, could this be the case why I have no internet connection when I enable it on the dialer interface? Is my only choice then to use ACLs on the interface?

Thanks

Louis

[raymong]

Be sure that CEF is enabled on your router (Unicast RPF relies on the FIB table generated by CEF). If that doesn't help, take a look through the following link which has some troubleshooting tips:

http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fsecur_c/fothersf/scfrpf.htm