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ecsnnsls
Beginner

ACI forwarding Question

Hello Experts,

I have a question on ACI forwarding. Below is the scenario,

 

Let's assume that all the endpoints are learnt and the respective tables are populated.

In VxLAN, when Leaf switch sends the VxLAN packet to the remote VTEP, the inner MAC points to RMAC of the remote VTEP. Once the encapsulation is done with the L3VNID and the outer headers, the packet is routed via the underlay.

Once the packet reaches the remote VTEP, it looks into the inner MAC and sees it's own MAC address and uses the L3VNID to locate the VRF and knows that it need to perform a routing operation in that VRF. I hope I have the right understanding. Please correct me if I am wrong.

 

In case of ACI, how does it work? When packet(to be routed) reaches the ingress leaf, the leaf knows to which VTEP it should forward the packet to. So it encapsulates this packet with the remote TEP IP and VRF VNID and routes the packet via the underlay. Now, does the ingress leaf VTEP modify the inner source and destination MAC? How does the remote TEP know that this packet needs to be routed?

Thanks

1 REPLY 1
Robert Burns
Cisco Employee

The basic functions (forwarding) between VXLAN standalone fabrics and ACI is fairly similar.  There's some additional policy logic that ACI adds, but at the end of the day, the overlay functions the same.  There's a great CiscoLive session that covers this in detail (video).  https://www.ciscolive.com/c/r/ciscolive/global/on-demand-library.html?search=ACI%20forwarding&search.solutions=scpsApplicationCentricInfrastructure#/session/1532976171045001Vj7G

There's also a complimentary whitepaper on endpoint learning that is worth the read.  https://www.cisco.com/c/en/us/solutions/collateral/data-center-virtualization/application-centric-infrastructure/white-paper-c11-739989.html 

Robert

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