300-420 Question 195
Select 3An enterprise network with multiple branch offices requires secure and scalable connectivity between branches over an MPLS service provider's network. The service provider recommends deploying MPLS Layer 3 VPNs. Which two components are required to ensure successful implementation of MPLS Layer 3 VPN in this scenario?
- A
Provider Edge (PE) routers must establish MP-BGP sessions to exchange VPNv4 routes.
- B
Customer Edge (CE) routers must run MPLS to communicate with the Provider Edge (PE) routers.
- C
Route Distinguishers (RDs) must be used to make VPN routes globally unique within the MPLS network.
- D
Route Targets (RTs) must be defined and imported/exported to control VPN route distribution.
- E
The MPLS service provider must deploy OSPF as the IGP between PE and CE routers.
Show answer and explanation
Correct answers: A, C, D
Explanation
MPLS Layer 3 VPNs rely on key components such as MP-BGP for route distribution, Route Distinguishers (RDs) for avoiding IP address conflicts, and Route Targets (RTs) for controlling route import/export policies. These components ensure scalability, isolation, and secure connectivity between customer sites. CE routers do not need MPLS, as it is implemented in the service provider's network, and the choice of routing protocol between PE and CE routers is flexible.
- A. Correct.
Correct: PE routers need to establish MP-BGP (Multiprotocol BGP) sessions to exchange VPNv4 or VPNv6 routes. This is a crucial aspect of MPLS Layer 3 VPNs, as MP-BGP is used to distribute customer routes across the service provider's MPLS backbone.
- B. Incorrect.
Incorrect: CE routers do not need to run MPLS. MPLS is implemented in the service provider's backbone, and CE routers typically use standard routing protocols (e.g., BGP, OSPF, or static routing) to communicate with PE routers.
- C. Correct.
Correct: RDs are required to differentiate overlapping IP address spaces between different VPNs. They ensure that customer routes are unique within the MPLS backbone, even if two customers use the same IP address ranges.
- D. Correct.
Correct: RTs are used to control the import and export of routes between VPNs. They determine which VPN routes are shared or isolated, ensuring proper route distribution based on policy.
- E. Incorrect.
Incorrect: While OSPF can be used as an IGP between PE and CE routers, it is not a mandatory requirement. Other routing protocols like BGP or static routing can also be used.