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Difficulty: HardNetwork Topology Architectures

A network engineer is designing a collapsed core enterprise campus topology connecting multiple access switches to a redundant pair of core switches. The design requires all redundant uplink interfaces from each access switch to forward traffic simultaneously for bandwidth optimization and load balancing, while preventing Layer 2 loops without forcing Spanning Tree Protocol (STP) to place any physical uplink into a blocking state. Which design architecture or technology satisfies these operational requirements?

  1. Implementation of multichassis link aggregation (such as Cisco StackWise or Virtual Switching System) across the collapsed core switchesAnswer
  2. B
    Enabling STP PortFast and BPDU Guard on all inter-switch trunk connections between the access switches and collapsed core switches
  3. C
    Deployment of bare-metal Type 1 hypervisors directly on access layer hardware to manage Layer 2 forwarding tables locally
  4. D
    Configuring access switches with unaggregated redundant access VLANs under the assumption that Layer 2 switches naturally isolate broadcast domains across physical uplinks

Answer

Implementation of multichassis link aggregation (such as Cisco StackWise or Virtual Switching System) across the collapsed core switches
In a 2-Tier Collapsed Core architecture, dual core switches operating independently would trigger Spanning Tree Protocol (STP) to block one of the redundant uplinks from each access switch to prevent Layer 2 loops. By deploying multichassis technologies such as Cisco StackWise, Virtual Switching System (VSS), or StackWise Virtual, the two core switches merge into a single logical control plane. This enables access switches to configure Multi-chassis EtherChannel (MEC), allowing all redundant physical uplinks to actively forward traffic simultaneously with balanced load distribution.

Step-by-Step Solution

1
Identify topology requirements
The topology is a 2-Tier Collapsed Core model requiring redundant uplinks from access switches to dual core switches with active-active forwarding (no STP blocked ports).
Standard STP blocks redundant paths to prevent loops, reducing aggregate bandwidth if links are unaggregated.
2
Evaluate switch virtualization and aggregation mechanisms
Multichassis technology presents dual core switches as a single logical STP bridge.
Because the access switch sees only one logical upstream device, cross-chassis EtherChannel (MEC/LACP) bundles all physical links into a single logical channel.
3
Confirm operational behavior
Traffic is load balanced across all links in the EtherChannel bundle while STP views the bundle as a single loop-free connection.
This achieves full bandwidth efficiency and instantaneous hardware-based failover.

Key Concept

Collapsed Core Topology & Multichassis EtherChannel (MEC / VSS / StackWise)
Estimated Time:2m 0s
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Topics

Network Topology Architectures

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