By default, a device does not generate or advertise a default route to its neighboring ISs. A default route is not advertised even if the device‘s IPv4 route table contains a default route. You can enable the device to advertise a default route to all neighboring ISs.
Note
This feature requires the presence of a default route in the IPv4 route table.By default, this feature originates the default route at Level 2 only. However, you can apply a route map to originate the default route to Level 1 only or at both Level 1 and Level 2. The route map must be configured before you can use the route map to configure the device to advertise the default route.