uRPF question

[cisconoobie]

How does unicast reverse path forwarding work when there is a default route in the FIB?

uRPF does a reverse check to make sure that the return sourced traffic can make it back through that same interface otherwise its dropped. Now what happens if its a spoofed source IP and uRPF checks the FIB and there is a default route? It still forwards it as usual, or am I confused?

[Harold Ritter]

Sparky,

The default route is not considered unless you configure the allow-default keyword as follow:

ip verify unicast source reachable-via any allow-default

Regards