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Question 18 - JN0-280 discussion

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Which statement is correct about a three-stage IP fabric underlay?

A.

Every ingress interface into the fabric is only two hops away from the egress interface.

Answers
A.

Every ingress interface into the fabric is only two hops away from the egress interface.

B.

Every spine device can communicate directly with other spine devices.

Answers
B.

Every spine device can communicate directly with other spine devices.

C.

Every leaf device can communicate directly with other leaf devices.

Answers
C.

Every leaf device can communicate directly with other leaf devices.

D.

Every server that connects to a three-stage IP fabric must be multihomed.

Answers
D.

Every server that connects to a three-stage IP fabric must be multihomed.

Suggested answer: A

Explanation:

In a three-stage IP fabric (also known as a Clos fabric), traffic between any two points (ingress to egress) in the fabric is only two hops away.

Step-by-Step Breakdown:

Three-Stage IP Fabric:

Leaf Layer: Leaf switches connect directly to servers and edge devices.

Spine Layer: Spine switches provide connectivity between leaf switches but do not connect to each other directly.

Two-Hop Communication:

In this architecture, every leaf switch is connected to every spine switch. Therefore, when a packet enters the fabric via an ingress leaf switch, it is forwarded to a spine switch, which then directs the packet to the correct egress leaf switch. This path always involves exactly two hops:

Ingress leaf Spine Egress leaf.

Benefits:

This consistent two-hop path ensures predictable latency and makes the network highly scalable while maintaining low complexity.

Juniper

Reference:

IP Fabric Architecture: This two-hop property of Clos fabrics is a hallmark of spine-leaf designs, as supported by Juniper's QFX and EX switches in data centers.

asked 10/10/2024
Simon John Mather
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