The Infrastructure VLAN is automatically configured during the Cisco ACI fabric discovery process. This VLAN, often referred to as the “infra VLAN,” is used to enable internal communication between the ACI fabric components, such as the leaf and spine nodes. It is vital for the overlay network and the control plane functionality. In the provided output, VLAN 3600 represents the Infrastructure VLAN, which is configured for inter-node communication.

 In Cisco Application Centric Infrastructure (ACI), when a subnet is configured on a bridge domain, the gateway IP address is configured on the leaf switches where the bridge domain of the tenant is present. This configuration allows for localized routing within the fabric, providing efficient east-west traffic handling without requiring traffic to traverse up to the spine nodes unless necessary for north-south routing or policy enforcement.

To prevent packet loss between the distributed virtual switch and the ACI fabric in a company’s ESXi infrastructure hosted on Cisco UCS-B Blade Servers, the vSwitch policy must implement MAC Pinning. This setting ensures that each virtual interface card (vNIC) on the UCS servers is pinned to an uplink Ethernet port, providing a stable and consistent path for traffic and preventing packet loss due to path changes.

To divert traffic between VM-1 and VM-2 using a Multi-Node service graph while preventing an insufficient number of available Layer 4 to Layer 7 devices in the first cluster, the following configuration set should be used:

PBR node tracking : This feature monitors the health of the nodes (Layer 4 to Layer 7 devices) in the service graph.  If a node becomes unavailable, the system can take action based on the tracking threshold 1 .

Tracking threshold with action bypass : When the number of healthy nodes falls below the tracking threshold, the action ‘bypass’ ensures that traffic is not sent to the unhealthy nodes, thus preventing service disruption 1 .

Symmetric PBR : This ensures that return traffic follows the same path as the original traffic, maintaining session consistency and avoiding asymmetric routing issues 1 .

Resilient hashing : This hashing mechanism provides a consistent and optimal distribution of traffic across the available Layer 4 to Layer 7 devices, even when the number of nodes changes due to a failure or maintenance 1 .

References  :=

Cisco APIC Layer 4 to Layer 7 Services Deployment Guide, Release 5.2(x)

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 sites 3 4 .

References  :=

Cisco Multi-Site Deployment Guide for ACI Fabrics 3

Cisco ACI Multi-Site Architecture White Paper 4

To enable the APIC in a Cisco ACI fabric using out-of-band management connectivity to access a routable host with an IP address of 192.168.11.2, you need to add a Fabric Access Policy that allows management connections. This involves configuring a contract that will be consumed and provided to your OOB devices. The contract will let the system know what traffic is allowed. In this case, you will use the default/common contract to permit any traffic.  This is necessary because the APIC needs to be able to send traffic to and receive traffic from the management network 1 .

References  :=

ACI: Configuring Out-of-Band (OOB) Access for Your Fabric - Cisco 1

Troubleshoot ACI Management and Core Services - In-band and Out-of-band Management - Cisco 2

To resolve the issue of STP convergence causing a microloop and significant CPU spike on all switches after connecting legacy non-ACI switches to the Cisco ACI fabric, BPDU filtering should be configured on the interfaces of the external switches that face the Cisco ACI fabric. BPDU filtering prevents Bridge Protocol Data Units (BPDUs) from being sent or received on those interfaces, which stops the STP process and eliminates the possibility of microloops.

For the new nodes in a Cisco ACI Multi-Pod deployment to be discoverable by the existing Cisco APICs, DHCP relay should be enabled on all links that are connected to Cisco ACI spines on Inter-Pod Network (IPN) devices. This allows the APICs to dynamically assign IP addresses to the new nodes, facilitating their discovery and integration into the fabric.

References  :=

Cisco ACI Multi-Pod Configuration Guide

Cisco ACI Best Practices Guide

 For Cisco ACI IPN (Inter-Pod Network) to manage multidestination traffic, multicast routing is a requirement. This is because multidestination traffic includes broadcast, unknown unicast, and multicast (BUM) traffic, which needs to be efficiently transported across different pods in a Cisco ACI Multi-Pod environment.  Multicast routing protocols like Bidirectional Protocol-Independent Multicast (Bidir PIM) are used to handle this type of traffic 1 .

References  :=

Cisco Application Centric Infrastructure Multi-Pod Configuration White Paper 1

On the egress leaf switch, when traffic is received from an L3Out,  no source MAC or IP address of the traffic is learned as a remote endpoint 1 .  The Cisco ACI fabric does not learn the IP addresses from the data plane in an L3Out domain; instead, it uses ARP to resolve next-hop IP and MAC relationships to reach the prefixes behind external routers 1 .