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Difficulty: Very hardNetwork Topologies and Types

An organization is deploying a multi-site network architecture connecting a main data center to six regional offices using a hybrid WAN model. To maximize resiliency and maintain continuous traffic routing, the core data center devices utilize a physical full-mesh topology, while the branch sites connect via a hub-and-spoke model. A network engineer is tasked with verifying the operational characteristics of this design. If two core switches in the data center full mesh fail simultaneously while a logical ring protocol operates over the physical topology, which outcome correctly describes the resulting fault tolerance and traffic behavior across the infrastructure?

  1. Traffic between remaining functional nodes in the data center full mesh will continue to route directly using remaining point-to-point links, but logical ring convergence failure will segment communications if the ring protocol lacks dual-ring redundancy.Answer
  2. B
    The entire network suffers a broadcast storm because VLAN broadcast domains automatically bridge across all physical mesh links upon node failure without Layer 3 isolation.
  3. C
    Branch spokes are isolated from the main data center because hub-and-spoke physical links must map 1:1 to OSI Layer 3 packets rather than Layer 2 frames.
  4. D
    All branch sites automatically lose access to default gateways because host IP addresses become unroutable when physical mesh links drop.

Answer

Traffic between remaining functional nodes in the data center full mesh will continue to route directly using remaining point-to-point links, but logical ring convergence failure will segment communications if the ring protocol lacks dual-ring redundancy.
In enterprise architecture, physical topology defines the actual cable layout and interconnection of nodes, while logical topology defines how data frames travel across the network. A physical full mesh ensures that surviving nodes retain direct point-to-point physical links. However, if a logical ring protocol runs over this infrastructure, the ring must successfully re-converge (or utilize counter-rotating ring mechanisms) to maintain logical communication flow when physical nodes fail.

Step-by-Step Solution

1
Analyze physical topology properties of a full mesh
A full mesh provides maximum physical redundancy with n(n−1)2\frac{n(n-1)}{2} direct connections. Failure of two nodes reduces total available paths but leaves redundant point-to-point connections between all surviving nodes.
Understanding physical mesh redundancy requires evaluating how link count and direct paths survive partial node failures.
2
Differentiate physical topology from logical topology behavior
The physical topology specifies physical cable links, while the logical topology dictates how signals and data frames travel across those physical paths (e.g., token passing or ring protocols).
Even with abundant physical links, logical protocols (like ring topologies) rely on specific path continuity and convergence mechanisms to handle node drops.
3
Evaluate combined fault tolerance
Physical links remain intact for active nodes, but logical ring token transmission requires protocol-level re-convergence or dual-ring counter-rotation to handle node removal.
Synthesizing physical mesh resiliency with logical overlay behavior yields the correct network survival outcome.

Key Concept

Physical vs. Logical Topologies and Redundancy Characteristics
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Topics

Network Topologies and Types

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