When trying to migrate a vmkernel from a vSwitch to a Nexus 1000v switch I got the error:
Operation failed, diagnostics report: A vmkernel nic for the connection point already exists.
The problem was that I could not see this vmkernel in the GUI.
To fix the problem I SSHed into the ESX which had the problem.
I ran the following command to list the vmkernels:
esxcli network ip interface list
In the list I could see a vmkernel connected to the Nexus 1000v that I could not see in the GUI.
I used the following command to remove it:
esxcli network ip interface remove --interface-name=vmk0
After I removed the vmkernel I could migrate it from the vSwitch to the Nexus 1000v with no errors.