300-620 Exam Dumps - Cisco CCNP Data Center Questions and Answers

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 attribute that should be configured for each user to enable RADIUS for external authentication in Cisco ACI is cisco-av-pair. This attribute allows for the assignment of roles and permissions to users authenticated via RADIUS.

The question asks which bridge domain setting is used when a Cisco ACI leaf switch learns the source IP address of a packet entering the front panel port. This involves understanding how ACI handles endpoint learning and IP address association within a bridge domain.

Requirement Analysis

When a packet enters a leaf switch’s front panel port, ACI learns the source IP and MAC address of the endpoint to populate its endpoint table.

The bridge domain settings control how IP addresses are learned and routed, especially for Layer 3 traffic.

The correct setting must enable the leaf switch to associate the source IP with the endpoint.

Option Evaluation

A. Unicast Routing:

The "Unicast Routing" setting in a bridge domain enables Layer 3 routing and allows the leaf switch to learn the source IP address of a packet by associating it with the MAC address and VLAN. When enabled, the switch performs IP-to-MAC mapping and updates the endpoint database, which is the standard mechanism for learning source IP addresses from incoming traffic.

To minimize possible traffic impact during the upgrade of an ACI fabric with 3 APIC controllers and servers dual-homed to pairs of leaf switches configured in VPC mode, the fabric should be upgraded following Option A2. This option involves creating two maintenance groups for the APIC controllers, upgrading one group at a time, and then proceeding with the leaf switches2. This staged approach helps ensure that not all paths are affected simultaneously, thereby reducing the potential for traffic disruption2.

 When the VMM resolution immediacy is set to pre-provision in a Cisco ACI environment, policies are downloaded to the ACI leaf switch regardless of Cisco Discovery Protocol neighborship1. This setting ensures that the policies are in place on the leaf switches even before a VM controller is attached to the virtual switch1.

An EPG is extended outside of the ACI fabric by statically assigning a VLAN ID to a leaf port in an EPG. This method maps the traffic received on the leaf port to the EPG, and the policy for this EPG is enforced

To break the STP loop between switch1 and switch2 in a Cisco ACI environment, enabling BPDU filtering on the interfaces facing the MST (Multiple Spanning Tree) switches is the necessary step. BPDU filtering prevents BPDUs from being sent or received through a port, which effectively stops the STP process on those ports and breaks the loop1.

When BPDU filtering is enabled on an interface, the switch does not send any BPDUs and ignores any BPDUs it receives on that interface. This can be used to prevent unwanted STP negotiations on ports where loops are not expected to happen or where STP is not desired1.

References :=

Use of ACI Operation with L2 Switches and Spanning Tree Link Types - Cisco1

ACI uses the SCP (Secure Copy Protocol) to securely save the configuration in a remote location. SCP is a network protocol that supports file transfers and relies on the Secure Shell (SSH) protocol to provide security for the transferred data.