What is a key difference between Layer 2 VPNs and Layer 3 VPNs?

The correct answer is A. Layer 2 VPNs encapsulate Ethernet frames in MPLS packets, and Layer 3 VPNs use labeled BGP. Layer 2 VPNs transport customer Ethernet frames transparently across the MPLS backbone by encapsulating the Layer 2 frame inside an MPLS pseudowire. Layer 3 VPNs, by contrast, distribute customer IP routes using MP-BGP, attaching MPLS labels to those IP prefixes so the provider…

Layer 2 VPNs

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ALayer 2 VPNs encapsulate Ethernet frames in MPLS packets, and Layer 3 VPNs use labeled BGP
BLayer 2 VPNs require the use of a Layer 2 forwarding plane with per-site MAC learning, and Layer
CLayer 2 VPNs can propagate VLAN tags across the MPLS network, and Layer 3 VPNs use BGP
DLayer 2 VPNs provide Layer 2 transport using pseudowires, and Layer 3 VPNs abstract Layer 2

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(16 responses)

A
94% (15)
C
6% (1)

Explanation

Layer 2 VPNs transport customer Ethernet frames transparently across the MPLS backbone by encapsulating the Layer 2 frame inside an MPLS pseudowire. Layer 3 VPNs, by contrast, distribute customer IP routes using MP-BGP, attaching MPLS labels to those IP prefixes so the provider core forwards packets based on labeled Layer 3 information rather than Layer 2 frames.

Topics

#Layer 2 VPN#Layer 3 VPN#pseudowire#MPLS encapsulation

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