What you need is a physical connection between the two "Internal" networks, i.e. another network adapter in your hosts (or VLANs configured, if your switch supports this) that you can use for this connection. I'm not sure whether a direct connection will work, or if you need to connect the two networks via a physical switch.
Would it be easy to migrate the VM which hosts vCenter to a different host?
That depends on your license, and/or storage. With local storage only, you will need at least Essentials Plus licensing to migrate powered on VMs. If you have shared storage, you may shut down the VM, remove it from the current host's inventoy, add it to the other host's inventory, and power it on again.
Thanks for the reply!
That's what I was afraid of. The "Internal" network is currently 100% virtual on a single host and as this is a lab using spare equipment, each host currently only has 1 single NIC used for the "Standard" network which are obviously connected via physical switch. My hope was that I could duplicate the "Internal" network on the 2nd host, then perhaps configure vCenter to connect the two "Internal" networks on both hosts using a virtual switch or something.
Based on your reply, perhaps this feature is available, but depends on the license. If so, what exactly would be required?
Unfortunately no, networks between hosts require a physical connection, unless someone invents a virtual network cable ;-)