Which mechanism provides Layer 2 fault isolation between data centers?

Question

Options

• Afabric path
• BOTV
• Cadvanced VPLS
• DLISP
• ETRILL

• A
  4% (1)
• B
  85% (23)
• C
  4% (1)
• E
  7% (2)

Explanation

OTV (Overlay Transport Virtualization) is Cisco's purpose-built technology for extending Layer 2 connectivity between geographically separated data centers while providing Layer 2 fault isolation between them. OTV encapsulates Layer 2 Ethernet frames within an IP/UDP overlay and carries them across a Layer 3 WAN or IP backbone. The critical isolation property is that OTV keeps STP domains entirely local to each site - STP BPDUs and Topology Change Notifications are NOT forwarded across OTV links. This means a bridging loop, STP reconvergence event, or broadcast storm at one data center cannot cascade across to the other. OTV also suppresses unknown unicast flooding across the DCI (data center interconnect) link. Choice A (FabricPath) and E (TRILL) are intra-data center fabric technologies that do not span between data centers. Choice D (LISP) is a Layer 3 protocol for host mobility and routing scalability, not Layer 2 extension. Choice C (advanced VPLS) can technically extend Layer 2 across data centers, but it merges STP domains across sites rather than isolating them, making it prone to propagating Layer 2 failures - it does not provide the fault isolation that OTV does.

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