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Cisco 300-620: How Does Cisco ACI Detect IP Address Changes for Silent Hosts?

By: Author Alex Lim

Posted on  - Last updated:

Categories Exam

Learn how Cisco ACI fabric detects the IP address of a silent host that moves locations without notifying the ACI leaf switch. Understand the role of endpoint announce messages and COOP protocol.

Table of Contents

Question

How does Cisco ACI detect the IP address of a silent host that moved from one location to another without notifying a Cisco ACI leaf?

A. Silent hosts are detected by the ACI fabric.
B. Endpoint announce messages are sent to COOP.
C. ARP requests are flooded in the bridge domain.
D. Bounce entries are installed on the leaf switch.

Answer

B. Endpoint announce messages are sent to COOP.

Explanation

When a silent host (an endpoint that does not use gratuitous ARP) moves from one location to another in a Cisco ACI fabric without notifying the ACI leaf switch, the fabric detects the host’s new location and IP address through endpoint announce messages.

Here’s how the process works:

  1. When a frame from the silent host arrives on an ACI leaf switch after it has moved, the leaf detects that the host has appeared in a new location.
  2. The leaf switch generates an endpoint announce message containing the host’s MAC address, IP address, encapsulation VNID and other identifying information.
  3. This endpoint announce message is sent via the COOP (Council of Oracle Protocol) to all the other leaf switches in the ACI fabric.
  4. The other leaves update their endpoint tables with the new location information for that host based on the COOP message.
  5. Traffic destined for the moved silent host can now be correctly forwarded by the fabric to its new location.

So in summary, it is the COOP protocol and endpoint announce messages, not the other listed mechanisms, that allow ACI to detect and handle location and IP changes for silent hosts. The fabric itself detects the move, announces it via COOP, and updates forwarding across all leaves.

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