Implementing Cisco Application Centric Infrastructure (DCACI) Free Sample Questions

When the Inter-Pod Network (IPN) does not support multicast, the ACI fabric must be configured to use ingress replication for BUM (Broadcast, Unknown Unicast, Multicast) traffic between pods. This is configured on the spine switches, which then use unicast to replicate and send the BUM traffic to all other remote pod VTEPs, bypassing the need for multicast in the IPN.

The Audit Log in ACI records all user-initiated configuration changes, providing traceability. A monitoring policy is required to define how these logs are handled.

To meet the long-term archival requirement, the audit logs must be sent to an external server. Configuring a Syslog destination within the monitoring policy is the standard method for exporting these logs.

A common mistake when deploying a service graph is failing to associate it with the contract that governs the traffic flow between the consumer (Web EPG) and provider (App EPG). The service graph template must be applied to the contract subject for the APIC to orchestrate the policy-based redirect (PBR) and steer the traffic through the service device.

When the default gateway for a BD exists outside the ACI fabric, the BD should be configured for Layer 2 extension only. This is achieved by not defining a subnet under the BD (which would create a pervasive gateway) and associating the BD with an L2Out policy. This allows Layer 2 frames to be forwarded out of the fabric to the external gateway.

A fundamental rule in the ACI object model is that an EPG must be associated with exactly one bridge domain. The bridge domain defines the Layer 2 forwarding context for the endpoints within that EPG. To have endpoints in different Layer 2 domains, you must create different EPGs.

For an L3Out to be fully functional and for routes to be exchanged, an External EPG (also known as an External Network Instance Profile) must be configured. This object is used to classify external networks and apply contracts. Without it, the L3Out is not complete, and routing protocol adjacencies may not form correctly or routes will not be exchanged.

Microsegmentation (uSeg) EPGs allow for the dynamic classification of endpoints based on their attributes. When integrated with a VMM domain like VMware vCenter, you can create rules based on various VM attributes, including 'VM Name', 'IP Address', 'OS', or custom attributes. This allows for automated policy assignment without manual intervention.

In the ACI object model, the Layer 2 forwarding construct (Bridge Domain) must be linked to the Layer 3 routing context (VRF). If the BD is not associated with a VRF, the fabric does not have a complete L2/L3 forwarding context, and endpoints will not be able to communicate, even within the same subnet, because essential functions like ARP are tied to this relationship.

The ACI firmware upgrade process involves two main components: a Firmware Group, which specifies the target firmware image, and a Maintenance Group, which contains the nodes to be upgraded and the schedule (or trigger) for the upgrade.

COOP is a zero-conf protocol used to communicate endpoint mapping information (IP/MAC/VRF to VTEP) to the spine switches. It ensures that all spines maintain a consistent copy of the mapping database, which is used for forwarding decisions. This allows any leaf to send traffic to a spine, which can then correctly forward it to the destination leaf.