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300-620 · Question #311

Refer to the exhibit. The Cisco ACI fabric is built with L2Out to the N9K1 and N9K2 switches. The switches run the RSTP protocol. The requirement is for the Cisco ACI fabric to detect loops from the…

The correct answer is B. Configure the N9K STP link type as a shared link. To enable the Cisco ACI fabric to detect and protect against loops from external N9K switches running RSTP via an L2Out, the STP link type on the N9K ports must be configured as a shared link. This ensures proper Spanning Tree Protocol interaction and BPDU processing for loop…

External Network Connectivity

Question

Refer to the exhibit. The Cisco ACI fabric is built with L2Out to the N9K1 and N9K2 switches. The switches run the RSTP protocol. The requirement is for the Cisco ACI fabric to detect loops from the N9K and for the fabric to be protected against loops. Which set of actions must be taken to meet the requirements?

Exhibit

300-620 question #311 exhibit

Options

  • AConfigure the N9K STP link type as point-to-point link.
  • BConfigure the N9K STP link type as a shared link.
  • CConfigure the N9K STP link type as a shared link.
  • DConfigure the N9K STP link type as a point-to-point link.

How the community answered

(16 responses)
  • A
    13% (2)
  • B
    81% (13)
  • D
    6% (1)

Why each option

To enable the Cisco ACI fabric to detect and protect against loops from external N9K switches running RSTP via an L2Out, the STP link type on the N9K ports must be configured as a shared link. This ensures proper Spanning Tree Protocol interaction and BPDU processing for loop detection.

AConfigure the N9K STP link type as point-to-point link.

Configuring the N9K STP link type as a point-to-point link optimizes convergence but can prevent the external switch from fully participating in STP, potentially hindering the ACI fabric's ability to detect and protect against loops from that segment.

BConfigure the N9K STP link type as a shared link.Correct

Configuring the N9K STP link type as a shared link ensures that the external switch participates fully in the Spanning Tree Protocol, sending and receiving BPDUs. This is essential for the ACI fabric, acting as the STP root, to properly detect loops originating from the N9K switches and to activate its own loop prevention mechanisms.

CConfigure the N9K STP link type as a shared link.
DConfigure the N9K STP link type as a point-to-point link.

Concept tested: ACI L2Out STP Integration and Loop Prevention

Source: https://www.cisco.com/c/en/us/td/docs/dcn/aci/apic/5x/l2-configuration/cisco-aci-layer-2-networking-configuration-guide-501/m-l2out.html

Topics

#L2Out#STP#Loop detection#External network connectivity

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