300-320 · Question #202
Which of these Layer 2 access designs does not support VLAN extensions?
The correct answer is B. loop-free U. The loop-free U design routes between distribution switches at Layer 3, which breaks the Layer 2 domain and prevents VLAN extension.
Question
Which of these Layer 2 access designs does not support VLAN extensions?
Options
- AFlexLinks
- Bloop-free U
- Clooped square
- Dlooped triangle
- Eloop-free inverted U
How the community answered
(24 responses)- A8% (2)
- B83% (20)
- C4% (1)
- D4% (1)
Why each option
The loop-free U design routes between distribution switches at Layer 3, which breaks the Layer 2 domain and prevents VLAN extension.
FlexLinks provides a redundant active/standby link pair as a STP-free alternative and maintains Layer 2 connectivity, supporting VLAN extension.
In the loop-free U topology, distribution switches are connected via Layer 3 routed links rather than Layer 2 trunks, which eliminates spanning tree loops but also creates a Layer 3 boundary that prevents VLANs from being extended across the distribution layer.
The looped square design maintains Layer 2 trunking throughout its topology, allowing VLANs to span across the design.
The looped triangle design uses Layer 2 trunks between access and distribution, preserving VLAN continuity and supporting extension.
The loop-free inverted U design keeps Layer 2 connectivity between access and distribution tiers, supporting VLAN extensions from access upward.
Concept tested: Layer 2 access topology VLAN extension support
Source: https://www.cisco.com/c/en/us/td/docs/solutions/Enterprise/Campus/campover.html
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