300-420 Question 160
Select 2A multinational corporation needs to connect branch offices across different regions using MPLS Layer 3 VPN. The network team has chosen to implement Route Distinguishers (RDs) and Route Targets (RTs) to ensure proper separation of VPNs and selective route sharing between specific sites. During the design phase, which of the following is a key consideration to achieve proper routing separation and route sharing across the MPLS L3VPN?
- A
Ensure each VRF has a unique RD to prevent route conflicts between overlapping IP address spaces.
- B
Use the same Route Target for exporting and importing routes across all VRFs to ensure consistent route sharing.
- C
Configure multiple RDs within a single VRF to allow different sites to use the same IP address space.
- D
Use Route Targets to define which routes are exported or imported between VRFs.
- E
Enable BGP as the routing protocol between the PE and CE routers to propagate VRF-specific routes.
Show answer and explanation
Correct answers: A, D
Explanation
MPLS Layer 3 VPN uses Route Distinguishers (RDs) to uniquely identify routes in scenarios where VPNs may have overlapping IP address spaces. Route Targets (RTs) are used to control the export and import of routes between VRFs, allowing selective route sharing. Configuring these correctly is critical to ensuring proper routing separation and meeting design requirements for inter-site communication.
- A. Correct.
Correct. RDs are used to distinguish routes in MPLS Layer 3 VPN environments, especially when overlapping IP address spaces are used. This ensures route separation between VPNs.
- B. Incorrect.
Incorrect. While Route Targets are essential for route sharing, using the same RT for all VRFs would result in all routes being shared across VPNs, which may violate the requirement for route separation.
- C. Incorrect.
Incorrect. Configuring multiple RDs within a single VRF is unnecessary and does not serve the purpose of IP address space separation. Each VRF typically has a single RD.
- D. Correct.
Correct. Route Targets define how routes are imported and exported between VRFs. Proper configuration of RTs ensures selective route sharing based on business requirements.
- E. Incorrect.
Incorrect. While BGP is commonly used as the PE-CE routing protocol, it is not directly related to routing separation or route sharing within the MPLS L3VPN framework.