In L3 Spine and Leaf design, which answer is correct?

Question

Options

• ALeaf switches connect to other leaf switches
• BEach leaf switch connects to each spine switch
• CEach spine switch connects to all other spine switches in a full mesh
• DLeaf switches connect to only one spine switch

• A
  3% (1)
• B
  93% (28)
• C
  3% (1)

Explanation

In a Spine and Leaf architecture, every leaf switch connects to every spine switch - this is the defining characteristic of the design, ensuring any two endpoints are always exactly two hops apart (leaf → spine → leaf), providing predictable, low-latency east-west traffic flows.

Why the distractors are wrong:

• A is wrong because leaf switches never connect to other leaf switches - that would reintroduce the spanning tree problems this design was built to eliminate.
• C is wrong because spine switches do not interconnect with each other either; they only connect downward to leaf switches, keeping the topology simple and scalable.
• D is wrong because connecting a leaf to only one spine would create a single point of failure and eliminate redundancy, defeating a core goal of the design.

Memory tip: Think of it like a bipartite graph - spines only talk to leaves, leaves only talk to spines, and every leaf-spine pair is connected. If you picture a grid, leaves are the rows, spines are the columns, and every intersection has a link.

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