Free Practice Questions for Cisco 300-620 Exam

To detect and prevent Layer 2 loops in a Cisco ACI fabric, the engineer must configure the Mis-Cabling Protocol (MCP) and related policies. MCP is designed to detect loops in Layer 2 network segments connected to ACI access ports and operates in conjunction with Spanning Tree Protocol (STP) running on external Layer 2 networks. The steps to accomplish these goals include:

Enable MCP Globally: Ensure that MCP is enabled globally on all access ports, virtual ports, and virtual port channels (VPCs) unless they are disabled at the individual port level1.

Configure MCP Transmit Frequency: Set the transmit frequency to a value that allows for quick loop detection. Starting with the 3.2(1) release, the Cisco ACI fabric provides faster loop detection with transmit frequencies from 100 milliseconds to 300 seconds1.

Set Action on Loop Detection: Decide how the MCP policies will act upon loop detection. Options include generating a syslog message or disabling the port upon detection of a loop1.

Implement Error Disabled Recovery Policy: Configure an error disabled recovery policy to automatically re-enable ports that were disabled due to loop detection after a configurable interval1.

By following these steps, the engineer can ensure that the Cisco ACI fabric will detect and prevent Layer 2 loops, thereby maintaining a stable and efficient network environment.

References :=

Cisco APIC Online Help - Loop Detection1

ACI Layer 2 loop detection and Mitigation - Cisco Video Portal2

 In the scenario where Server A is connected to the Cisco ACI fabric using teamed interfaces with one active and one standby, enabling ARP flooding in the bridge domain configuration is necessary to resolve the issue that occurs when the standby interface becomes active and uses its built-in MAC address to send traffic. Enabling ARP flooding allows the fabric to learn the new MAC address without waiting for the ARP timeout, which helps to ensure that traffic continues to flow to the correct destination after a failover event1.

References :=

Discuss Cisco 300-620 Exam Topic 9 Question 71 | Pass4Success1

When a bridge domain is configured with the hardware-proxy option for Layer 2 unknown unicast traffic, if the spine switch is unable to find the MAC address in the proxy database, it will drop the Layer 2 unknown unicast packet4. This behavior is controlled by the hardware proxy option associated with a bridge domain4.

When designing two data centers based on Cisco ACI technology that can extend L2/L3, VXLAN, and network policy across locations with ACI Multi-Pod, the two requirements that must be considered are:

A single APIC Cluster is required in a Multi-Pod design4.

ACI Multi-Pod requires an IP Network supporting PIM-Bidir2.

In a Cisco ACI environment with multiple silent hosts that are often relocated between leaf switches, configuring IP Data-Plane Learning to ‘No’ will minimize the relocation impact and make the ACI fabric relearn the new location of the host faster. Disabling IP Data-Plane Learning prevents the fabric from learning IP addresses from the data plane, which can speed up the process of relearning host locations when they move3.

 To determine if a change in the behavior of the ACI fabric was due to human intervention, an ACI administrator should inspect the audit logs in the APIC UI. The audit logs provide a record of all user events, which includes actions performed by users, making it possible to trace any changes back to specific human activities1.

 When creating a subnet within a bridge domain in Cisco ACI, the configuration option used to specify the network visibility of the subnet is the scope12. The scope can be set to private, public, or shared, determining how the subnet is advertised and accessed within and outside of the ACI fabric12.

To configure communication between the EPGs in different tenants, the subnet scope should be set to “Shared between VRFs”. This allows the subnet to be shared across different VRFs, enabling communication between EPGs that are in different tenants but within the same VRF. By marking the subnet as shared, it becomes visible to other VRFs, which is necessary for inter-tenant communication1.

References :=

Learning ACI - Part 12: Inter-VRF and Inter-Tenant Communication