CCNP Data Center 300-620 Updated Exam

To configure a Cisco ACI system to detect network loops for both untagged and tagged traffic and to stop the loop by disabling an interface within 4 seconds, the following configuration must be used:

Enable Mis-Cabling Protocol (MCP): MCP detects loops from external sources and will err-disable the interface on which Cisco ACI receives its own packet. This is crucial for preventing loops in the network1.

Configure MCP Transmit Frequency: Set the MCP transmit frequency to a value that allows for quick loop detection. The Cisco ACI fabric provides faster loop detection with transmit frequencies from 100 milliseconds to 300 seconds. To meet the requirement of detecting and stopping a loop within 4 seconds, you would set the transmit frequency to a value less than 4 seconds2.

Set Action on Loop Detection: Configure the MCP policies to identify loops and decide how to act upon them. You can set the policy to generate a syslog message or disable the port upon loop detection2.

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 interval2.

By implementing these configurations, the Cisco ACI system will be able to detect and stop network loops quickly and efficiently, ensuring network stability and preventing potential disruptions.

References :=

Cisco APIC Online Help - Loop Detection2

Cisco ACI Best Practices Quick Summary

 In Cisco ACI, a contract is used to define the communication policy between EPGs (Endpoint Groups). It specifies which types of traffic are allowed to pass between EPGs and can include filters for protocols, ports, and other attributes. In the context of the logical system design, the contract would be the object that completes the communication requirements as indicated by the dotted line in the exhibit12.

References :=

Cisco Application Centric Infrastructure (ACI) Design Guide1

Cisco ACI Policy Model Guide2

In the context of VMM, the protocol between ACI leaf and compute hosts that ensures that the policies are pushed to the leaf switches for immediate and on-demand resolution immediacy is LLDP (Link Layer Discovery Protocol)2. LLDP is used for discovery and to ensure that the policies are applied as needed for the virtual machines2.