To which switch or switches should you provide redundant links in order to achieve high availability with reliable fast convergence in the enterprise campus?

Question

Options

• Ato a core switch running Cisco NSF and SSO from redundant distribution switches connected with
• Bto a core switch running Cisco NSF and SSO from redundant distribution switches connected with
• Cto two core switches from redundant distribution switches connected with a Layer 2 link
• Dto two core switches from redundant distribution switches connected with a Layer 3 link
• Eto two core switches running Cisco NSF and SSO from two redundant distribution switches

• A
  11% (3)
• C
  4% (1)
• D
  81% (22)
• E
  4% (1)

Explanation

For high availability with reliable fast convergence in the enterprise campus, the recommended design is redundant distribution switches connecting via Layer 3 (routed) links to two core switches (Choice D). Layer 3 links allow IP routing protocols (such as EIGRP or OSPF) to detect failures and reconverge in sub-second timeframes-far faster than Layer 2 Spanning Tree Protocol (STP), which can take 30–50 seconds to converge. Choices A and B appear truncated but generally refer to a single core switch, which is a single point of failure. Choice C uses Layer 2 links, which rely on STP and converge slowly. Choice E, while it mentions NSF/SSO, does not specify Layer 3 links. Layer 3 routed links between distribution and core are the key design element enabling rapid convergence.

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