Cisco
352-001 · Question #278
352-001 Question #278: Real Exam Question with Answer & Explanation
The correct answer is C: Replace VPLS with a Layer 3 MVPN solution to carry the streams between sites.. EoMPLS VPLS floods multicast like broadcast to all pseudowires, making it unscalable for high-bandwidth multicast across 100 sites; Layer 3 MVPN uses multicast distribution trees to deliver traffic only to interested receivers.
Question
An MPLS service provider is offering a standard EoMPLS-based VPLS service to Customer A, providing Layer 2 connectivity between a central site and approximately 100 remote sites. Customer A wants to use the VPLS network to carry its internal multicast video feeds, which are sourced at the central site and consist of 20 groups at 5 Mb/s each. Which service provider recommendation is the most scalable?
Options
- AEoMPLS-based VPLS already carries multicast traffic in a scalable manner.
- BReplicate the multicast traffic on the P routers.
- CReplace VPLS with a Layer 3 MVPN solution to carry the streams between sites.
- DUse GRE tunnels to carry the streams between sites.
Explanation
EoMPLS VPLS floods multicast like broadcast to all pseudowires, making it unscalable for high-bandwidth multicast across 100 sites; Layer 3 MVPN uses multicast distribution trees to deliver traffic only to interested receivers.
Common mistakes.
- A. EoMPLS VPLS treats multicast as BUM traffic and floods it across all pseudowires to every site, consuming 100 Mb/s of replicated bandwidth per site and making the design extremely unscalable at 100 remote sites.
- B. Replicating multicast on P routers does not eliminate the flooding behavior of VPLS; traffic would still be sent to all sites regardless of group membership, providing no scalability benefit.
- D. GRE tunnels create point-to-point overlays that require the source to individually replicate each stream per tunnel, providing no multicast-awareness and no scalability improvement over standard VPLS flooding.
Concept tested. MVPN vs VPLS multicast scalability design
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