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400-007 · Question #208
400-007 Question #208: Real Exam Question with Answer & Explanation
The correct answer is B: MPLS over BGP over multipoint GRE. MPLS over BGP over multipoint GRE satisfies all three requirements by using enterprise-owned GRE tunnels as SP-independent transport, MP-BGP as the VPNv4 control plane, and advertising only loopback addresses to the SP.
Question
Refer to the exhibit. An architect must design an enterprise WAN that connects the headquarters with 22 branch offices. The number of remote sites is expected to triple in the next three years. The final solution must comply with these requirements: - Only the loopback address of each of the enterprise CE X and Y routers must be advertised to the interconnecting service provider cloud network. - The transport layer must carry the VPNv4 label and VPN payload over the MP-BGP control plane. - The transport layer must not be under service provider control. Which enterprise WAN transport virtualization technique meets the requirements?
Exhibit
Options
- AEIGRP Over the Top
- BMPLS over BGP over multipoint GRE
- CDMVPN per VRF
- Dpoint-to-point GRE per VRF
Explanation
MPLS over BGP over multipoint GRE satisfies all three requirements by using enterprise-owned GRE tunnels as SP-independent transport, MP-BGP as the VPNv4 control plane, and advertising only loopback addresses to the SP.
Common mistakes.
- A. EIGRP Over the Top uses EIGRP as the overlay routing protocol and does not use MP-BGP to carry VPNv4 labels and VPN payload, failing the control plane requirement.
- C. DMVPN per VRF uses GRE tunnels with NHRP and typically uses EIGRP or OSPF as the overlay routing protocol - it does not natively implement an MP-BGP VPNv4 control plane over the transport layer.
- D. Point-to-point GRE per VRF does not scale for 22 branches growing to 66 or more because each new branch requires dedicated tunnel interfaces on all other routers, creating an unmanageable configuration burden.
Concept tested. Enterprise WAN virtualization with MPLS over BGP over multipoint GRE
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