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

In a two-pod Cisco ACI Multi-Pod environment, it is recommended to deploy no more than two Cisco APIC controllers in the same pod to avoid losing all replicas of a shard if a pod fails. The APIC cluster is a distributed system where each APIC contains a replica of the configuration database, referred to as a shard. If all replicas of a shard were located in the same pod and that pod were to fail, it would result in the loss of the shard and potentially impact the entire fabric’s operation. By distributing the APIC controllers across pods, the risk of losing all replicas due to a single point of failure is mitigated, enhancing the overall resiliency of the system1.

References :=

ACI Multi-Pod White Paper - Cisco1

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

To ensure that destination updates from a newly created L3Out are propagated to all Cisco ACI leaf switches, a BGP route reflector policy should be applied. This policy allows the border leaf switches, which act as BGP route reflectors, to redistribute the learned routes to other leaf switches within the fabric1.

 In the context of ACI Multi-Site, the information of an endpoint (MAC/IP) that belongs to site 1 is advertised to site 2 using the EVPN control plane as soon as the endpoint is discovered in one site. This allows for immediate visibility of the endpoint across sites.

When the client endpoint and the service node interface are in different subnets, the Adjacency Type value should be set to Routed. This setting is used to indicate that routing is required between the client endpoint and the service node interface, as they are not in the same Layer 2 broadcast domain and need Layer 3 routing to communicate.

In Cisco ACI, a leaf switch learns a source IP or MAC as a remote endpoint when VXLAN traffic arrives on a leaf fabric port from the spine, and the inner source IP is within the range of the bridge domain subnets associated with the leaf. This process is part of the ACI’s COOP (Council Of Oracles Protocol), which ensures that endpoint information is accurately disseminated across the fabric for efficient traffic forwarding.

ACI Multi-Site architecture is designed to interconnect geographically dispersed data centers and extend Layer 2 and Layer 3 connectivity between those locations with consistent policy enforcement. It allows for either a single APIC cluster to manage multiple ACI sites or supports a dedicated APIC cluster per site. This architecture ensures a scalable and flexible approach to managing multiple data center sites, providing a unified policy framework and operational model across the sites34.

References :=

Cisco Multi-Site Deployment Guide for ACI Fabrics3

Cisco ACI Multi-Site Architecture White Paper4

 In a Cisco ACI fabric, the spine switches are typically configured as route reflectors. This is because spine switches are central to the fabric’s architecture and are responsible for interconnecting all the leaf switches, making them ideal for reflecting BGP routes within the fabric. Therefore, the components that should be configured as route reflectors are:

Spine1 (Option A)

Spine2 (Option C)

To support a new application that is sensitive to latency and jitter and sets the DSCP values of packets to AF31 and CS6, it is necessary to align the ACI Quality of Service (QoS) levels and Inter-Pod Network (IPN) QoS policies. This alignment ensures that the DSCP values are preserved and respected across the ACI fabric and the IPN, preventing packets from being delayed or dropped between pods.

References :=

Cisco ACI Multi-Site Architecture White Paper

Cisco ACI Best Practices Guide

Cisco ACI Quality of Service Configuration Guide