Which two statements describe primary differences between MPLS Layer 2 and Layer 3 VPNs? (Choose two.)
Click on the arrows to vote for the correct answer
A. B. C. D. E.BD.
MPLS (Multiprotocol Label Switching) is a technology used to create virtual private networks ( VPNs) in service provider networks. MPLS VPNs can be categorized into two types: Layer 2 VPN and Layer 3 VPN.
Layer 2 VPNs:
Layer 2 VPNs provide point-to-point connections between the customer sites over the MPLS service provider network. In Layer 2 VPN, customer traffic is encapsulated in MPLS labels instead of IP packets. Layer 2 VPNs are also referred to as Virtual Private Wire Service (VPWS).
AToM (Any Transport over MPLS) is used to provide point-to-point Ethernet-based Layer 2 VPNs over MPLS. In AToM, the customer Ethernet frame is encapsulated in MPLS labels and transported over the MPLS network to the remote PE (Provider Edge) router, where it is de-encapsulated and delivered to the destination customer site.
Layer 3 VPNs:
Layer 3 VPNs provide a more flexible and scalable VPN solution as compared to Layer 2 VPNs. Layer 3 VPNs use BGP (Border Gateway Protocol) to distribute the customer routes across the MPLS network. In Layer 3 VPNs, customer traffic is encapsulated in MPLS labels as well as IP packets. Layer 3 VPNs are also referred to as Virtual Private Routed Network (VPRN) or Virtual Private Network ( VPNv4).
MPLS/BGP is used to provide Layer 3 VPNs. In MPLS/BGP, customer routes are advertised between the PE routers using BGP. The PE routers add MPLS labels to the IP packets and forward them over the MPLS network to the remote PE router, where they are de-encapsulated and delivered to the destination customer site.
To summarize, the primary differences between Layer 2 and Layer 3 MPLS VPNs are:
Encapsulation: Layer 2 VPNs encapsulate customer traffic in MPLS labels only, while Layer 3 VPNs encapsulate customer traffic in MPLS labels and IP packets.
Routing: Layer 2 VPNs use AToM for point-to-point Ethernet-based VPNs, while Layer 3 VPNs use MPLS/BGP for more flexible and scalable VPN solutions.
Therefore, the correct answers are B and E:
B. Layer 2 VPNs use AToM, but Layer 3 VPNs use MPLS/BGP.
E. Layer 2 VPNs use IPsec tunneling, but Layer 3 VPNs use pseudowires to provide tunneling. (Note: The correct statement should be "Layer 2 VPNs use pseudowires to provide tunneling" instead of "Layer 2 VPNs use IPsec tunneling.")