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350-501 · Question #48

Which statement about the overlay VPN model is true?

The correct answer is C. The overlay model provides the ability to reduce the amount of routing state that core routers. The overlay VPN model allows core routers to maintain a significantly smaller routing table by only needing to route the provider's infrastructure addresses, as customer routes are encapsulated.

Architecture

Question

Which statement about the overlay VPN model is true?

Options

  • AThe overlay model demands a lot from provisioning because when adding one customer site, it
  • BThe overlay model does not scale to the same size as the MPLS VPN model.
  • CThe overlay model provides the ability to reduce the amount of routing state that core routers
  • DThe overlay model provides privacy and isolation between the different customers by using

How the community answered

(31 responses)
  • A
    6% (2)
  • B
    3% (1)
  • C
    87% (27)
  • D
    3% (1)

Why each option

The overlay VPN model allows core routers to maintain a significantly smaller routing table by only needing to route the provider's infrastructure addresses, as customer routes are encapsulated.

AThe overlay model demands a lot from provisioning because when adding one customer site, it

While provisioning for the customer edge might increase (e.g., full mesh tunnels), the statement is incomplete and generally for the *provider core*, the overlay model simplifies provisioning regarding routing state.

BThe overlay model does not scale to the same size as the MPLS VPN model.

Overlay models, especially full-mesh tunnel designs, often face scalability limitations compared to provider-managed MPLS VPNs due to higher complexity on customer/edge devices and N-squared provisioning challenges.

CThe overlay model provides the ability to reduce the amount of routing state that core routersCorrect

In an overlay VPN model, the service provider's core routers are only responsible for forwarding encapsulated customer traffic based on the outer (provider) IP header. They do not need to carry specific customer routes in their routing tables, thus reducing the routing state within the core network.

DThe overlay model provides privacy and isolation between the different customers by using

Overlay models do provide privacy and isolation, typically through encapsulation (e.g., GRE, IPsec) or separate routing instances, but the statement is incomplete.

Concept tested: Overlay VPN model characteristics

Source: https://www.oreilly.com/library/view/mpls-based-vpns/0596008985/ch01.html

Topics

#Overlay VPN#Routing state#Core network#VPN architecture

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