A BGP router can only advertise an EBGP learned route，provided that the route is an IGP route in the routing table.
A BGP router can only advertise an IBGP learned route，provided that the route is an IGP route in the routing table.
A BGP router can only advertise an IBGP learned route，provided that the route is an IGP route that is not in the routing table.
A BGP router can only advertise an EBGP learned route，provided that the route is a metric of 0 in the BGP table.