ACI Host Tracking ARP Request Count

Answer Correct answer: C — Leaf switches send three ARP requests.

How many ARP requests are sent from leaf switches to perform host tracking for local endpoints?

1
2
3 Correct Answer
4

cisco aci host tracking arp requests local endpoints endpoint aging

Community Votes

60%

40%

60% of anonymous learners picked answer C. Votes are pick records left by other test-takers — they are not the verified answer.

Community Insight

The question tests knowledge of ACI host tracking behavior, specifically the default number of ARP probes sent before an endpoint is considered aged out, often confused with single packet glean learning.

This page explains Cisco ACI host tracking for local endpoints and determines the number of ARP requests sent by leaf switches to verify endpoint presence. It clarifies the 75% aging interval behavior.

Choosing A (1) is a common mistake because learners confuse the initial ARP Glean packet used for learning with the subsequent verification process used during host tracking, which involves multiple retries.

Community Discussion (6 comments)

ashwind123 👍 1 Selected: C

its 3.

prospio971 👍 1 Selected: C

In Cisco ACI, host tracking is a mechanism used to ensure that local endpoints (e.g., hosts or VMs) remain active in the fabric's endpoint table. If no traffic is received from a local endpoint during a certain period (75% of the aging interval), the ACI leaf switch performs host tracking by sending three ARP requests to verify the endpoint's presence. https://www.cisco.com/c/en/us/solutions/collateral/data-center-virtualization/application-centric-infrastructure/white-paper-c11-739989.html

samfab 👍 1 Selected: C

For local endpoints that have IP addresses associated with them, leaf switches perform Host Tracking at 75 percent of the aging interval if no packets from the same IP address was received during the interval. Host Tracking is always enabled and will send three ARP requests to the IP address in order to make sure that the IP address is still responsive.

designated 👍 1 Selected: A

Cisco ACI uses silent host detection to monitor endpoints that do not generate traffic. The ACI leaf switch sends a single ARP Glean request to detect and track local endpoints. This mechanism is efficient and avoids unnecessary flooding in the network.

Rollizo 👍 1 Selected: A

In a network with host tracking capabilities (such as in Cisco ACI environments), leaf switches send 1 ARP request to track each local endpoint. This single ARP request is used to determine the MAC and IP information for the local endpoint, which helps maintain accurate endpoint information in the network's host tracking tables.

Habtamu 👍 1

I will go with A

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Expert Analysis

Why the Answer Is Correct

In Cisco ACI, host tracking is triggered at 75% of the endpoint aging interval when no traffic is seen from the endpoint. To verify the IP endpoint is still active, the leaf switch sends three ARP requests. This is the standard default behavior to ensure reliability before removing the entry.

Why the Other Options Are Wrong

Option A (1) is incorrect because a single request is insufficient for reliable verification in a busy network; it might be confused with the initial glean learning mechanism. Options B (2) and D (4) do not match the default configuration parameters for host tracking probes in ACI.

Community Comment Notes

User prospio971 correctly identified that "three ARP requests" are sent at 75% of the aging interval to verify presence. Some users, like designated, mistakenly suggested a single ARP Glean request, likely conflating the learning process with the host tracking verification process.

Exam Strategy

Remember the specific threshold for host tracking in ACI is 75% of the aging time. Associate this with the number 3 for the default ARP probe count to distinguish it from single-packet glean learning.

Related Analysis

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