Refer to the exhibit The engineering team noticed route disruptions when DSL subscriber 172.16.20.10 goes offline. In this service provider environment:

The OSPF backbone area is configured to advertise loopback prefixes

The PE routers are running BGP-IPv4 address family in a BGP-free core topology.

The DSL subscriber IP subnet 172.16.20.10/32 is redistributed in BGP on PE1

Which configuration on PE1 resolves the issue?