@HeiniGut wrote: I was hoping that I could have the host machine on the network, but ensure that the guest legacy machines was never connected to the network.

In that case you may have a couple of options, one related to VMware Workstation/Player, and, or the other to the 'legacy guest' itself [operating system unknown] . . . 

VMware: In the legacy guests Virtual Machine Setting - Hardware tab, Remove the 'Network Adapter'

Legacy Guest: from within the legacy guests operating system, disable the network interface/s, and restrict access to it.