300-620 Exam Dumps - Implementing Cisco Application Centric Infrastructure (300-620 DCACI)

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

The advantage of implementing an active-active firewall cluster that is stretched across separate pods when anycast services are configured is that local traffic within a pod is load-balanced between the clustered firewalls. This means that traffic destined for the anycast IP address of the service node (firewall) will preferentially be directed to the local node within the same pod, thus optimizing traffic flows and reducing latency by avoiding unnecessary traffic tromboning to a remote pod1.

 To redistribute externally learned OSPF routes within the ACI fabric, a Route Control Profile must be configured1. This profile allows for the control of route redistribution and the application of route maps to influence routing decisions within the fabric1.

Storm control should be configured on port channel on a single leaf switch (Option B) and endpoint-facing trunk interface (Option D) to protect against broadcast traffic6. These interfaces are where storm control policies are typically applied to prevent disruptions caused by traffic storms6.

When a pre-provision immediacy is used, the policy is downloaded to the Cisco ACI leaf switch and programmed into the hardware policy Content Addressable Memory (CAM) as soon as the change is implemented on the Cisco Application Policy Infrastructure Controller (APIC). This means that the policy is ready on the leaf switch before any endpoints are actually connected.

 In a Cisco ACI Multi-Pod environment with active-active data centers and active-standby firewalls in each data center, enabling Pod ID Aware Redirection is the action that should be taken to maintain traffic symmetry through the firewalls. This feature ensures that traffic is consistently directed through the active firewall based on the pod identifier, thus maintaining the desired traffic flow and symmetry2.

References :=

Cisco ACI Multi-Pod and Service Node Integration White Paper

When configuring a Multi-Pod system with the default gateway residing outside of the ACI fabric for a bridge domain, the setting that should be configured is to disable Limit IP Learning to Subnet (Option A). This allows the ACI fabric to learn IP addresses outside of the defined subnet, which is necessary when the default gateway is external.