Full Mesh WAN: Informed Decisions and Always-On Backup Paths

300-420 By islever Editorial Last updated

Design high availability for enterprise WAN for on-premises, hybrid, and cloud solutions

Short answer

A A full mesh lets every node see all routes (informed decisions), keeps a backup path always available, and uses a suboptimal path only after a failure.

Question

An architect must design a topology for a WAN network that satisfies these requirements: • Devices must be able to make informed decisions. • Suboptimal paths are allowed only in case of a failure. • Backup paths must always be available. Which topology must the architect select?
  1. full mesh Correct Answer
  2. Clos
  3. partial mesh
  4. hub and spoke

Key Takeaways

Full mesh = maximum path diversity and no single point of failure, matching 'backup paths always available' and 'suboptimal only on failure'. Hub-and-spoke fails the 'always available backup' test (hub is a SPoF).

A full-mesh WAN connects every site to every other site. Each device has full routing knowledge (informed decisions), a backup path to every peer always exists, and traffic only takes a suboptimal path when a primary link fails. Partial mesh/hub-and-spoke have single points of failure.

Common mistake: Picking D (hub and spoke): the hub is a single point of failure, so backup paths are NOT always available — directly contradicting the requirement. Partial mesh (C) has fewer backups than full mesh.

Expert Analysis

Why the Answer Is Correct

A is correct. A full mesh gives every node a direct link to every other node, so each makes informed routing decisions with full topology knowledge, always has a backup path, and only uses a suboptimal path after a failure.

Why the Other Options Are Wrong

C (partial mesh) and D (hub-and-spoke) have fewer paths and single points of failure, so backup paths are not always available. B (Clos) is a data-center fabric topology, not a WAN branch topology for this requirement.

Community Comment Notes

The vote is A (100). Commenters state full mesh is the only option where backup paths are always available; hub-and-spoke fails because the hub is a single point of failure.

Community Votes

A
100%

100% of anonymous learners picked answer A. Votes are pick records left by other test-takers — they are not the verified answer.

Discussion 3 contributions

Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.

From public community threads 3

  1. PicoOstrava 👍 3 Answered A
    D. Hub and Spoke: This topology is the least ideal because it has a single central hub to which all spokes are connected. If the hub fails, all spokes lose connectivity. While it may have a backup path in some designs, it's not as resilient as a full mesh.
  2. muffedtrims 👍 3 Answered A
    Full mesh, is the only option for backup paths must always be available
  3. Seb82 👍 4 Answered A
    Full mesh

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