ACI - Migration scenario

Hello People,

So we basically are going to move from a NX-OS network to an ACI Fabric. Now i've been through the stuff about ACI and have done a lot of reading and poc labbing.

But i have forgotten a few parts of the lab that are very crucial (silly me). Chief amongst is the migration from the old network to the ACI fabric. Now Cisco has written a very formal document on this:

https://www.cisco.com/c/en/us/td/docs/switches/datacenter/aci/apic/sw/migration_guides/migrating_existing_networks_to_aci.html

And everything looks clear and concise but i still linger with a few questions:

Let me tell you first that i work in a shared team, but i'm dedicated on a project. The goal of this project is to migrate the customer rescources of the shared fabric (NX-OS) to their own dedicated network (Cisco ACI).

This means that i have to involve other people that manage the shared NX-OS Fabric and they have expressed concerns that we should not connect the Cisco ACI fabric L2 to the NX-OS network as it may cause a loop in the network. I do agree on this but i think steps can be taken to minimize this risk. (I know that the ACI does not actually talk spanning-tree, it doesn't even respond to the BPDU's i think, but it can bridge a BPDU)

Is my assumption correct to say, if we define the L2 links towards the ACI as type edge's and leave them out of the STP calculations that we cannot cause a loop because ACI won't send a BPDU towards the legacy network? However it won't drop the BPDU as wel, so what's there to stop the BPDU going across the ACI and back into the legacy network. I would assume proper cabling and connection thinking goes into that.

Also has anyone done a migration of this with an ESXi Host, loads of scenario's describe that we can connect an ESXi Host to the ACI Fabric and migrate the Servers like this, this would include that the ESXi host has spare ports to be configured in ACI fabric and the vlan's only have port level significance. Did anyone perform a migration like this? How fluent is it? What were the caveats you ran into.

Thanks in advance, I hope that people can share their real life migration story here so i can get an idea of how it all works.