Cooperation with default route

When a default route exists, all packets that fail to match a specific IPv6 FIB entry match the default route during IPv6 uRPF check and thus are permitted to pass. If you allow using the default route (by using allow-default-route), IPv6 uRPF permits packets that only match the default route. By default, IPv6 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 device. If you enable IPv6 uRPF on a CE that has a default route pointing to the PE, select the allow-default-route keyword.