GARP in ACI

[netbeginner]

Hi All, 

What is the use cases and role of GARP (Gratuitous ARP) in Cisco ACI, I searched a lot on Internet and finding a one example everywhere which does'nt tell all about the same . Would like to know more on the use cases and requirement.

How it works in ACI. Why it is required. 

Is this recommended to enable GARP on ACI always. Will there be any limitation or long term adverse impact due to enabling of GARP.

What are the other factors which need to be taken care & keep in mind before enabling GARP.

Rgds

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[netbeginner]

Hey Guys, 

Requesting if someone come up to clear the points.

Rgds

[Sergiu.Daniluk]

Hello my friend,

Just to make sure I understand your question, do you refer to enabling GARP on your servers or the "GARP based detection" feature on ACI BD?

Cheers,

Sergiu

[netbeginner]

Hi MSD,

I am requesting for sharing some practical use cases for GARP requirement, i mean where GARP use is recommended.

[Sergiu.Daniluk]

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.

Take care,

Sergiu