Which network design principle should be followed to improve Layer 2 stability in an enterprise campus design?

Question

Options

• AExtend all user VLANs throughout the access layer.
• BExtend all user VLANs throughout the core layer.
• CExtend only required user VLANs throughout the access layer.
• DExtend only required user VLANs throughout the aggregation layer.

• A
  7% (3)
• B
  4% (2)
• C
  87% (40)
• D
  2% (1)

Explanation

Layer 2 Stability in Enterprise Campus Design

Extending only required user VLANs throughout the access layer (Option C) is correct because limiting VLAN propagation reduces the Spanning Tree Protocol (STP) domain size, minimizes broadcast traffic, and contains Layer 2 failures to smaller network segments - all of which directly improve stability.

Why the distractors are wrong:

• Option A is wrong because extending all VLANs access-wide creates unnecessarily large broadcast domains and increases STP complexity, making the network more prone to instability.
• Option B is wrong because user VLANs should never be extended into the core layer - the core is meant for fast, efficient transit routing, not VLAN termination.
• Option D is wrong because the aggregation (distribution) layer is where VLANs are typically terminated (via Layer 3 routing), not extended; propagating VLANs there defeats this purpose.

Memory Tip: Think "Right VLANs, Right Place" - keep VLANs local to the access layer and only where needed. The golden rule is: the smaller the Layer 2 domain, the more stable and manageable the network.

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