Cooperation with default route

When a default route exists, all packets that fail to match a specific FIB entry match the default route during uRPF check and thus are permitted to pass. To avoid this situation, you can disable uRPF from using any default route to discard such packets. If you allow using the default route (set by using allow-default-route), uRPF permits packets that only match the default route. By default, uRPF discards packets that can only match a default route. Typically, you do not need to configure the allow-default-route keyword on a PE device because it has no default route pointing to the CE. If you enable uRPF on a CE that has a default route pointing to the PE, select the allow-default-route keyword.