Single-Homed Full Mesh Gives HA Without Extra WAN Links

300-420 By islever Editorial Last updated

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

Short answer

B One WAN interface per router means single-homed; a full mesh over the WAN service gives path diversity and high availability without extra WAN links.

Question

Refer to the exhibit. Due to budget constraints, a customer decided to purchase WAN routers with one LAN and one WAN interface per device. There is a requirement to connect the three sites to ensure high availability without buying additional WAN links. Which design deployment must the customer choose? - Exhibit: Single-Homed Full Mesh Gives HA Without Extra WAN Links
  1. dual-homed full mesh
  2. single-homed full mesh Correct Answer
  3. single-homed hub-and-spoke
  4. dual-homed hub-and-spoke

Key Takeaways

One WAN interface per device = single-homed. A full mesh over the WAN transport provides backup paths logically; dual-homed (A/D) would need extra WAN links the budget forbids.

Each router has only one WAN interface, so the sites are single-homed to the WAN service. Running a full mesh over that service provides any-to-any connectivity and logical path diversity, delivering high availability without purchasing additional WAN links (which dual-homing would require).

Common mistake: Picking C (hub-and-spoke): it has a single point of failure at the hub and less path diversity than a full mesh; the requirement for HA with backup paths points to full mesh (B), not hub-and-spoke.

Expert Analysis

Why the Answer Is Correct

B is correct. The one WAN interface per device means each site is single-homed to the provider. A full mesh over the WAN service yields any-to-any reachability and logical path diversity, so high availability is achieved without procuring extra WAN links.

Why the Other Options Are Wrong

A and D (dual-homed) require additional WAN links, which the budget constraint rules out. C (hub-and-spoke) creates a hub single point of failure and less path diversity than the full mesh the HA requirement implies.

Community Comment Notes

The vote is B (56) vs C (44). The top comment notes one WAN link means single-homed, and with no defined hub a full mesh adds no extra cost while meeting HA.

Community Votes

B
56%
C
44%

56% of anonymous learners picked answer B. Votes are pick records left by other test-takers — they are not the verified answer.

Discussion 4 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 4

  1. 935608e 👍 4 Answered B
    One WAN-Link -> Single homed No hub location defined -> full mesh Full mesh does not create additional cost
  2. Seb82 👍 2 Answered C
    I cannot see how D is an option, considering that each router has only one LAN and one WAN port
  3. Swiz005 👍 2 Answered C
    Definitely C - There is budget constraints
  4. chaba7654321 👍 1 Answered B
    Agree with 935608e

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