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 ASBRterminated 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.