Refer to the exhibit. An engineer must use Cisco ThousandEyes testing to monitor their Cisco Catalyst SD-WAN fabric. Which SD-WAN component is being monitored by ThousandEyes?

Question

Options

• Aunderlay
• BIPsec tunnels
• Coverlay
• DGRE tunnels

• A
  94% (29)
• B
  3% (1)
• C
  3% (1)

Explanation

Option A is correct because Cisco ThousandEyes is deployed specifically to provide visibility into the underlay - the physical transport network (broadband, MPLS, LTE circuits) that the SD-WAN fabric runs on top of. ThousandEyes agents run on SD-WAN edge devices and measure real-time path metrics (latency, loss, jitter) across these physical links, giving the SD-WAN controller the intelligence it needs for optimal path selection.

Why the distractors are wrong:

• C (overlay): The overlay is the logical SD-WAN network (policies, virtual paths) built on top of the underlay - vManage already has native visibility into this layer, so ThousandEyes isn't needed there.
• B (IPsec tunnels) and D (GRE tunnels): Both are encapsulation mechanisms that exist within the overlay, not separate monitoring targets. ThousandEyes operates beneath the tunnel layer to assess the raw transport health.

Memory tip: Think "ThousandEyes looks UNDER the hood." Just like a mechanic checks the engine (underlay) rather than the car's paint job (overlay), ThousandEyes inspects the physical transport paths that everything else depends on.

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