BGP4+ obtains the routing information inside the AS by importing the IGP routing information and advertises the route to the peer. Before the IGP routing information is imported, related configuration should be made to allow BGP4+ to import default routes.
bgp { as-number-plain | as-number-dot }
ipv6-family unicast
import-route protocol [ process-id ] [ med med | route-policy route-policy-name ] *
If the default-route imported command is not used, you cannot import the default routes from other protocols by using the import-route command.