ACI Data-Plane Endpoint Learning Attributes

300-620 By islever Editorial Last updated

Describe endpoint learning Implement bridge domain configuration settings such as unicast routing, Layer 2 unknown unicast, ARP flooding

Short answer

AD The leaf switch programs Remote MAC/IP from tunneled traffic and Local MAC/IP from ingress traffic when default data-plane learning is active.

Question

A Cisco ACI bridge domain and VRF are configured with a default data-plane learning configuration. Which two endpoint attributes are programmed in the leaf switch when receiving traffic? (Choose two.)
  1. Remote MAC, IP Correct Answer
  2. Remote Subnet
  3. Local IP, not MAC
  4. Local MAC, IP Correct Answer
  5. Local Subnet
  6. Remote IP

Key Takeaways

The trap is confusing 'subnet' policies with 'endpoint' bindings; ACI learns specific MAC+IP pairs, not subnets, distinguishing between local (ingress) and remote (tunneled) sources.

This question tests ACI bridge domain endpoint learning. With default data-plane IP learning enabled, leaf switches program Local MAC/IP and Remote MAC/IP attributes into the endpoint table.

Common mistake: Selecting B or E because students confuse the BD subnet configuration (a static policy) with the dynamic endpoint entries (MAC/IP pairs) that are actually learned and programmed in the leaf switch hardware.

Expert Analysis

Data-Plane Learning Mechanics In Cisco ACI, the default configuration for a Bridge Domain (BD) includes data-plane IP address learning. This feature allows the leaf switch to dynamically learn endpoint information by inspecting incoming traffic packets rather than relying solely on control-plane protocols like ARP.

Local vs. Remote Endpoint Attributes When a leaf switch receives a packet from an unknown endpoint, it performs the following actions based on the source:

  • Local Endpoints: If the traffic originates from a port within the fabric (or is locally connected), the leaf learns the Local MAC address and Local IP address directly from the data plane. This corresponds to option D.
  • Remote Endpoints: For traffic coming from external sources or other fabrics via VXLAN tunneling, the leaf switch extracts the MAC address from the inner Ethernet header and the IP address from the IP header. These are programmed as Remote MAC and Remote IP entries in the endpoint table. This corresponds to option A.

Why Other Options Are Incorrect

  • Subnets (B, E): The endpoint table stores individual endpoint bindings (MAC/IP pairs), not subnet ranges. Subnet configurations are policy objects, not learned endpoint attributes.
  • Partial Entries (C, F): In standard data-plane learning scenarios, both Layer 2 (MAC) and Layer 3 (IP) information are captured together to form a complete endpoint identity. Learning only the IP (F) or only the MAC without the associated IP (not explicitly offered as a pair here) does not reflect the standard "Local MAC, IP" or "Remote MAC, IP" binding behavior described in ACI documentation.

Operational Consequence If data-plane IP learning were disabled, remote endpoints would only be learned via ARP replies (control plane), leading to slower convergence and potential flooding of ARP requests. With it enabled (default), the network achieves rapid, automatic endpoint discovery for both local and remote entities.

Official Reference

https://www.cisco.com/c/en/us/products/collateral/networking/cloud-networking/application-centric-infrastructure/fabric-endpoint-learning-wp.html

This link opens the official vendor documentation in a new tab.

Exam Strategy

Always check if 'data-plane IP learning' is enabled or disabled in the scenario. If enabled (default), expect full MAC+IP learning for both local and remote endpoints. If disabled, focus on control-plane mechanisms like ARP flooding and resolution immediacy. Eliminate any option mentioning 'Subnet' as an learned attribute, as subnets are configured policies, not learned endpoint identities.

Frequently Asked Questions

What happens if data-plane IP learning is disabled?

Remote endpoints are only learned via ARP replies (control plane). The leaf switch will not extract IP addresses from data packets, which can lead to increased ARP flooding and slower endpoint convergence.

Does ACI learn Subnets in the endpoint table?

No. Subnets are configured as static policies within a Bridge Domain. The endpoint table stores individual dynamic bindings of MAC addresses to IP addresses for specific hosts.

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Community Votes

D
50%
F
30%
A
20%

50% of anonymous learners picked answer D. Votes are pick records left by other test-takers — they are not the verified answer.

Discussion 7 contributions

Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.

From public community threads 7

  1. frzzt 👍 7
    It can also be Remote MAC,IP because it depends if it is Routerd or switched traffic.. The question sucks
  2. designated 👍 3
    A and D are correct: When dataplane IP address learning is enabled (which is the default setting) for a VRF instance, local and remote MAC addresses are learned using an endpoint-to-endpoint ARP request.
  3. 7korn7 👍 3
    The key point is default data-plane learning configuration
  4. sailorsoul 👍 2
    remote point can only be either ip address or mac address.
  5. designated 👍 1
    Notes: When dataplane IP address learning is disabled, all the remote IP address entries in the tenant VRF instance are removed. The local IP entries are aged out and, subsequently, will not be re learned through the dataplane, but can still be learned from the control plane. • When dataplane IP address learning is disabled, already learned local IP endpoints are retained and require control plane refreshes (ARP) to be kept alive (assuming IP aging is also enabled). Dataplane Layer 3 traffic will not keep IP endpoints alive. https://www.cisco.com/c/en/us/td/docs/dcn/aci/apic/6x/l3-configuration/cisco-apic-layer-3-networking-configuration-guide-60x/dataplane-ip-learning-per-vrf-layer3-config-60x.pdf
Show 2 more comments
  1. ostych 👍 1
    Local endpoint: Section "Cisco ACI leaf switch follows these steps to learn a local endpoint MAC address and IP address" It learns both IP and MAC from ARP or data plane packet. Remote endpoint: Cisco ACI leaf switch follows these steps to learn a remote endpoint MAC or IP address. So either MAC or IP learns as remote depending whether VXLAN contains BD or VRF information. https://www.cisco.com/c/en/us/products/collateral/networking/cloud-networking/application-centric-infrastructure/fabric-endpoint-learning-wp.html#Remoteendpointlearning
  2. namenicknickname 👍 1
    https://www.cisco.com/c/en/us/products/collateral/networking/cloud-networking/application-centric-infrastructure/fabric-endpoint-learning-wp.html

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