As shown in the figure, PE1 and PE2 exchange private network route information with their respective CEs through OSPF, and the same domain ID is configured on PE1 and PE2. Which of the following LSA types may be transmitted to CE2 when PE2 imports BGP routes to the OSPF process?
When PE routers (PE1 and PE2) exchange routes using BGP and then import these routes into OSPF for their respective CEs, the type of LSA transmitted depends on the domain IDs configuration. Because PE1 and PE2 have the same domain ID, the OSPF process will advertise inter-area routes, which uses Type 3 LSAs to communicate with CE routers. Type 5 LSAs are used for external routes from outside the OSPF autonomous system, and Type 7 LSAs are applicable for NSSA areas translating into Type 5 at the ABR. Therefore, the correct LSA type transmitted to CE2 when PE2 imports BGP routes to the OSPF process is Type 3 LSA.
Before advertising the remote routes sent by BGP to CEs, PEs need to determine the type of OSPF routes (Type 3, Type 5, or Type 7) to be advertised to CEs based on domain IDs. If local domain IDs are the same as or compatible with remote domain IDs in BGP routes, PEs advertise Type 3 routes. Otherwise, Type 5 or Type 7 routes are advertised.
Before advertising the remote routes sent by BGP to CEs, PEs need to determine the type of OSPF routes (Type 3, Type 5, or Type 7) to be advertised to CEs based on domain IDs. If local domain IDs are the same as or compatible with remote domain IDs in BGP routes, PEs advertise Type 3 routes. Otherwise, Type 5 or Type 7 routes are advertised.