You may get warning (13921) after migration of a virtual machine from a host to cluster:

Let’s check virtual network adapters of the virtual machine:

As you see, I have 5 network tags. But the “Internal Network” exist in the Cluster? Let’s check it.

Right click to Cluster and click to Properties. Click “Networks” tab.

Now I see only 4 network cards. So where is the “Internal Network”?

That means I don’t have any network called “Internal Network”. So I have to create Internal Network in all Clustered Hosts or I have to choose another network. I simply choose Backup Network for my virtual machine.

Tadaaaa! We fixed it :) Remember, in order to assign a virtual network to virtual machine in a cluster environment, you need to create that virtual network in all hyper-v hosts. Good luck.