Exam 300-620 topic 1 question 212 discussion

Although Cisco ACI can detect MAC and IP address movement between leaf switch ports, leaf switches, bridge domains, and EPGs, it does not detect the movement of an IP address to a new MAC address if the new MAC address is from the same interface and same EPG as the old MAC address. When the GARP based detection option is enabled, Cisco ACI will trigger an endpoint move based on GARP packets if the move occurs on the same interface and same EPG. If a GARP packet comes from the same interface and same EPG, then endpoint learning is triggered only when Unicast Routing, ARP Flooding, and “GARP based detection” are all enabled for the bridge domain. https://www.cisco.com/c/en/us/solutions/collateral/data-center-virtualization/application-centric-infrastructure/white-paper-c11-739989.html

I agree

GARP is used to update IP to MAC relation on upstream network devices. It is most relevant in case of vmotions or VMs/servers moving from one host to another, and the MAC address changes, but the IP remains the same. In the context of ACI, the leaf switches can detect MAC and IP address movement between leaf switch ports, leaf switches, bridge domains, and EPGs, but it does not detect the movement of an IP address to a new MAC address if the new MAC address is from the same interface and same EPG as the old MAC address. When the GARP based detection option is enabled (configuration available under the BD), Cisco ACI will trigger an endpoint move based on GARP packets if the move occurs on the same interface and same EPG. If a GARP packet comes from the same interface and same EPG, then endpoint learning is triggered only when Unicast Routing, ARP Flooding, and “GARP based detection” are all enabled for the bridge domain.