Lucy. > To use MPLS LSP tunnel, option B requires pre-build MPLS > LSP tunnel between two PEs that belong to different ASes, which requires two > SPs pre-provisioning process that may not apply to here.
Incorrect. Option B does not require "pre-build MPLS LSP tunnel between two PEs that belong to different ASes" - that would be option C. In fact option B does not require any pre established LSP or IP tunnel between PE-PE. Option B ASBR set's next hop self on VPNv4/v6 routes hence it terminates any corresponding transport encapsulation used in it's own domain. Cheers, R.
