300-440 Question 167
Select 3A service provider is implementing MPLS Layer 3 VPN to provide connectivity between two customer sites. The provider wants to ensure traffic separation between customers and allow for overlapping IP address spaces. Which mechanisms in MPLS Layer 3 VPN ensure these requirements are met?
- A
Route Distinguishers (RDs)
- B
Route Targets (RTs)
- C
Label Distribution Protocol (LDP)
- D
Multiprotocol BGP (MP-BGP)
- E
Provider Edge (PE) routers enabling OSPF between customer sites
Show answer and explanation
Correct answers: A, B, D
Explanation
MPLS Layer 3 VPN achieves traffic separation and support for overlapping IP address spaces by leveraging Route Distinguishers (RDs) to make prefixes unique, Route Targets (RTs) to control route distribution between VRFs, and Multiprotocol BGP (MP-BGP) to exchange VPNv4 routes between PE routers. While LDP is essential for label switching in the MPLS core, it does not directly address these specific requirements. Similarly, enabling OSPF between customer sites is not necessary in MPLS Layer 3 VPN, as the PE routers use VRFs and MPLS protocols for traffic isolation.
- A. Correct.
Route Distinguishers (RDs) are used to make identical IP address prefixes unique in the MPLS VPN environment, ensuring traffic separation for overlapping IP spaces.
- B. Correct.
Route Targets (RTs) are used to control the import and export of routes between VRFs, which is critical for maintaining traffic separation in MPLS Layer 3 VPNs.
- C. Incorrect.
Label Distribution Protocol (LDP) is used for label switching in the MPLS core, but it does not directly address traffic separation or overlapping IP spaces.
- D. Correct.
Multiprotocol BGP (MP-BGP) is used to exchange VPNv4 routes between PE routers, ensuring proper route propagation for each VPN and enabling traffic separation.
- E. Incorrect.
Provider Edge (PE) routers do not require enabling OSPF between customer sites; instead, they use VRFs and MPLS protocols to maintain separation.