Which flavor of MPLS Layer 3 VPN has MPLS enabled on PE-CE links?

The correct answer is B. CSC. CSC (Carrier Supporting Carrier) is correct because in this architecture, the CE device is itself a carrier's PE router running MPLS, so the backbone carrier must enable MPLS on the PE-CE link to exchange labels and support the customer carrier's labeled traffic end-to-end…

Layer 3 VPNs

Question

Options

Abasic
BCSC
Cinter-AS
DAToM
EVPLS

How the community answered

(56 responses)

A
2% (1)
B
88% (49)
C
2% (1)
D
4% (2)
E
5% (3)

Explanation

CSC (Carrier Supporting Carrier) is correct because in this architecture, the CE device is itself a carrier's PE router running MPLS, so the backbone carrier must enable MPLS on the PE-CE link to exchange labels and support the customer carrier's labeled traffic end-to-end.

Basic L3 VPN (A) uses standard IP routing protocols (BGP, OSPF, etc.) on PE-CE links - no MPLS there; labels only appear in the provider core. Inter-AS (C) extends L3 VPNs across AS boundaries between ASBRs, but still does not require MPLS on the PE-CE link itself. AToM (D) is a Layer 2 transport technology (not L3 VPN at all) that tunnels L2 frames like Frame Relay or Ethernet over an MPLS backbone. VPLS (E) is also a Layer 2 VPN service providing multipoint Ethernet bridging over MPLS - again, not an L3 VPN flavor.

Memory tip: Think "CSC = carrier serving a carrier" - since your customer IS a carrier running their own MPLS network, the link connecting you to them must speak MPLS. If the CE is just a regular enterprise router, no MPLS on that link is needed.

Topics

#MPLS L3VPN#Carrier Supporting Carrier#PE-CE Architecture#VPN Flavors

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