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QuestionQ302

Network Design

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Refer to the table. A customer is evaluating connectivity options for a DCI between two production data centers. The solution must deliver dual 10G connections between the locations with no single points of failure for Day 1 operations. It must also offer the ability to scale to up to 20 resilient connections in the second year to support isolated SAN over IP and isolated dedicated replication IP circuits. All connectivity methods are duplex 10 Gbps. Which transport technology has the lowest two-year cost for this scenario?

  • A CWDM
  • B DWDM
  • C MPLS
  • D Metro Ethernet
Explanation

DWDM provides the wavelength density needed to carry twenty isolated, resilient 10-Gb/s connections over redundant dark-fiber paths; a 40-channel DWDM implementation can allocate two independent wavelength paths to each connection. This removes single-path dependence while avoiding the per-circuit service cost of scaling MPLS or Metro Ethernet. CWDM has materially lower channel density and does not meet the required scale. Cisco documents DWDM implementations with 40 channels and CWDM implementations supporting only up to eight channels.

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