300-420 Question 162
Select 3A company has a multi-site network connected through an MPLS Layer 3 VPN provided by their service provider. The network design requires communication between different sites while maintaining separate routing tables for each customer. Which of the following components are essential for the MPLS Layer 3 VPN solution to function correctly?
- A
Provider Edge (PE) routers with VRF instances configured
- B
Route Distinguishers (RDs) to ensure unique prefixes per customer
- C
Label Distribution Protocol (LDP) for MPLS label distribution on the provider backbone
- D
Customer Edge (CE) routers running BGP with the service provider
- E
Provider (P) routers configured with OSPF for customer routes
Show answer and explanation
Correct answers: A, B, C
Explanation
MPLS Layer 3 VPNs rely on specific components and configurations to function correctly. PE routers with VRFs isolate customer routing tables, RDs ensure unique prefixes per customer, and LDP handles label distribution in the MPLS backbone. While CE routers can use BGP or other routing protocols to communicate with PE routers, and P routers do not need to handle customer-specific routing protocols, the three listed components are essential for MPLS Layer 3 VPN functionality.
- A. Correct.
Correct: PE routers with VRF instances are essential for isolating customer routing tables and enabling MPLS Layer 3 VPN functionality.
- B. Correct.
Correct: RDs ensure unique prefixes for each customer, which is a key requirement for MPLS Layer 3 VPNs.
- C. Correct.
Correct: LDP is essential for distributing MPLS labels in the provider backbone, enabling end-to-end routing across the MPLS network.
- D. Incorrect.
Incorrect: While BGP is often used between CE and PE routers, it is not a strict requirement; other routing protocols like OSPF or static routes can also be used.
- E. Incorrect.
Incorrect: P routers do not hold customer routing information and are not required to run OSPF for customer routes. They only handle label switching in the MPLS core.