352-001 Question #274: Real Exam Question with Answer & Explanation

The correct answer is C: OTV. OTV (Overlay Transport Virtualization) is the correct Layer 2 tunneling technology for data center interconnect over an IP-only WAN, as it is purpose-built for VM mobility across geographically separated sites.

Question

A company would like to distribute a virtual machine (VM) hosting cluster between three data centers with the capability to move VMs between sites. The connectivity between data centers is IP only and the new design should use the existing WAN. Which Layer 2 tunneling technology do you recommend?

Options

AVPLS
BL2TPv3
COTV
DAToM

Explanation

OTV (Overlay Transport Virtualization) is the correct Layer 2 tunneling technology for data center interconnect over an IP-only WAN, as it is purpose-built for VM mobility across geographically separated sites.

Common mistakes.

A. VPLS requires an MPLS-enabled core network to operate, making it incompatible with an IP-only WAN without adding MPLS infrastructure.
B. L2TPv3 can tunnel Layer 2 over IP but is a point-to-point technology that lacks the MAC-routing intelligence and native multi-site scalability required for VM mobility across three data centers.
D. AToM (Any Transport over MPLS) requires MPLS as its underlying transport mechanism, which directly contradicts the IP-only WAN constraint.

Concept tested. OTV for Layer 2 DCI over IP transport

Reference. https://www.cisco.com/c/en/us/td/docs/solutions/Enterprise/Data_Center/DCI/whitepaper/DCI3_OTV_Design.html

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