Cisco Updated 300-620 Exam Questions and Answers by maira

MisCabling Protocol (MCP) detects loops from external sources (i.e., misbehaving servers, external networking equipment running STP, etc.) and will err-disable the interface on which ACI receives its own packet. Enabling this feature is a best practice, and it should be enabled globally and on all interfaces, regardless of the end device. For MCP to be enabled, you need to have it enabled globally and on a per-interface basis. While MCP is enabled on all interfaces by default, it is not turned “on” until you also enable it globally. The global configuration knob for MCP can be enabled by configuring the global settings here: Fabric > Access Policies > Global Policies > MCP Instance Policy default. https://www.cisco.com/c/dam/en/us/solutions/collateral/data-center-virtualization/application-centric-infrastructure/aci-guide-using-mcp-mis-cabling-protocol.pdf

To enable communication between the external subnet and internal EPG1, and to allow L3Out traffic to leak into the VRF named “VF1”, the following configuration set should be used:

External Subnets for External EPG: This configuration defines the subnets that are external to the ACI fabric but need to be reachable from within the fabric. It is necessary to specify which subnets are to be considered part of the L3Out1.

Shared Route Control Subnet: This setting allows the subnets to be shared across different VRFs, enabling communication between EPGs that are in different tenants but within the same VRF1.

Shared Security Import Subnet: This configuration ensures that the security policies (contracts) associated with the shared subnets are also imported, allowing for the necessary traffic to flow between the internal and external endpoints1.

By applying this configuration set, the external subnet and internal EPG1 will be able to communicate, and the L3Out traffic will be properly leaked into the designated VRF, meeting the specified goals.

References :=

ACI Inter VRF/Tenant Route Leaking Configuration Example1

In a Cisco ACI fabric, Spanning Tree Protocol (STP) Bridge Protocol Data Units (BPDUs) that are generated by an external switch, such as Switch2 in this scenario, are indeed forwarded across the fabric. This allows externally connected switches to maintain a loop-free topology. While Cisco ACI does not participate in STP as it uses its own protocols and mechanisms for loop prevention within the fabric, it will forward STP BPDUs across End Point Groups (EPGs) on which they are received1. This ensures that the connected external switches can still use STP for their loop prevention mechanisms.

References :=

Cisco Community Discussion on STP BPDUs in ACI1