By configuring BGP to import default routes, you can import the IGP default routes that already exist in the local routing table.
To import a default route, the default-route imported command needs to be used together with the import-route command. The default route cannot be imported using only the import-route command. The default-route imported command is used only to import the default route that exists in the local routing table.
bgp { as-number-plain | as-number-dot }