OK, now lets really get going. Lets talk about how you could possibly start migrating FEXs to ACI.
Firstly, we need to discuss the basics of the application-centric approach and the network-centric approach. In the network centric model, you can connect ACI to a legacy network that is still running significant vlans. This is a decent strategy if you don't want to re-ip as you move to ACI and have a significant 7k-5k-2k deployment today.
Read more HERE
Although ACI is capable of handling this type of infrastructure, it was obviously not designed to maintain a deployment this way from the GUI so we will need to compensate with a significant amount of scripting.
This example was actually created to support some B22 migrations. For each of these migrations every one of the ports was configured identically and as a trunk.
I created a .txt file that I could read from for the vlans that needed to get added to the trunk. You can create your own with a "show vlan b | i active" on an existing 5k/7k that you are migrating from. I will include an example of what that looks like after the script.