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Difficulty: MediumNetwork Topology Architectures

An organization is upgrading its campus network architecture. The network engineering team needs to design an access-to-distribution layer interconnect that provides active-active path utilization across all uplinks, sub-second routing convergence, and complete elimination of Spanning Tree Protocol (STP) blocked ports. Which network topology design best satisfies these requirements?

  1. Extending Layer 3 routing to the access layer to establish a Routed Access architecture.Answer
  2. B
    Enabling STP PortFast on the inter-switch trunk links connecting access switches to distribution switches.
  3. C
    Deploying Type 2 hypervisors on access switches to manage Layer 2 frame forwarding and loop prevention.
  4. D
    Installing Layer 2 switches at the distribution tier to divide single network segments into separate broadcast domains.

Answer

Extending Layer 3 routing to the access layer to establish a Routed Access architecture.
In a Routed Access architecture, Layer 3 routing functions are extended down to the access layer switches. By making the access-to-distribution uplinks Layer 3 routed interfaces, Spanning Tree Protocol is eliminated on those connections. Traffic can be load-balanced using Equal-Cost Multi-Path (ECMP), and routing protocols provide fast convergence without blocked links.

Step-by-Step Solution

1
Analyze the requirements for active-active uplinks, fast convergence, and STP elimination.
Traditional Layer 2 access-to-distribution designs require STP to block redundant links, preventing active-active forwarding and resulting in slower convergence.
Layer 2 topologies with redundant paths must block ports via STP to avoid loops.
2
Evaluate the impact of shifting the Layer 2/Layer 3 boundary to access layer switches.
Running Layer 3 routing on access switches converts uplinks to point-to-point IP links.
Routed links utilize routing protocols (such as OSPF or EIGRP) for path selection, permitting ECMP load balancing and eliminating Layer 2 loops and STP entirely.

Key Concept

Routed Access Layer Campus Architecture
Estimated Time:1m 30s
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Topics

Network Topology Architectures

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