Most likely when you start moving to an ACI fabric you’re not going to forklift your entire network and put in a new one. That’s just not realistic. More likely you will start migrating lines of business or certain applications to ACI, but these applications will need to be able to communicate with end point devices in your legacy network. We can do this in a couple different ways, depending on what needs we have. We can have a layer 3 external or layer 2 external (or both). For this article I’m going to go through the layer 2 external access configuration. We might need this for anything that requires extending VLANs, high availability, things like database clusters, or custom applications that may not consider layer 3.
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