A service provider requests more details about the recent Inter-AS MPLS VPN Option B configuration that was recently deployed. Consider this configuration:
router bgp 3717
address-family vpnv4 unicast retain route-target all
commit
!
Which option describes why this particular command is needed?
A. The ASBR can have many working customer VRFs, so this configuration ensures the coexistence of all the route-target extended communities that belong to the all ASBR-terminated customer VRFs.
B. When implementing the Inter-AS Option B MPLS VPN solution, all the route targets that are transmitted over the Inter-AS links need an ASBR local database to forward the customer traffic correctly.
C. The Inter-AS Option B design implements VPNv4 communication over the Inter-AS link, hence the requirement for a route-target association for each customer VPN connected across two or more ASs.
D. In the Inter-AS Option B design, no local VRF is maintained on the ASBR routers,so the default behavior of the operating system is to deny any route-target extended community that is encoded in the incoming iBGP updates. This configuration permits VPNv4 communication by accepting the iBGP updates even if no route targets are configured locally.
