A customer has two sites over an MPLS cloud with Ethernet connections and requires one STP domain to be transparent over the MPLS provider. Which label-switching technology can the provider use…

Question

Options

• AL2TPV3
• BEoMPLS
• CVPLS
• DH-VPLS

• A
  3% (1)
• B
  72% (23)
• C
  9% (3)
• D
  16% (5)

Explanation

EoMPLS (Ethernet over MPLS) creates a point-to-point pseudowire between two PE routers, encapsulating Ethernet frames directly in MPLS labels and forwarding them without inspecting Layer 2 content - meaning the provider never needs to learn customer MAC addresses, and STP BPDUs pass through transparently as part of a single logical domain.

Why the distractors are wrong:

• A. L2TPv3 uses IP as its transport mechanism, not MPLS label switching - it fails the "label-switching technology" requirement in the question.
• C. VPLS is multipoint-to-multipoint and does require provider PE routers to learn customer MAC addresses to perform MAC-based forwarding within the service instance.
• D. H-VPLS is simply a hierarchical extension of VPLS that improves scalability - it still requires MAC learning at the provider edge, same disqualifier as VPLS.

Memory tip: Think of EoMPLS as a "dumb pipe" - it just slaps an MPLS label on the Ethernet frame and ships it, no questions asked. VPLS/H-VPLS are "smart switches in the cloud" that must learn MACs to do multipoint forwarding; EoMPLS is just a point-to-point label-switched wire that stays out of your Layer 2 business.

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