There is one physical underlay with contains the following:

the Hypervistor Host $($your physical machine running workstation$)$

additional physical hosts,

and a SOHO router that is also a DHCP Server $($denoted by the "bull horn" icon$)$

There is only one broadcast domain at this moment, B$1,$ and it spans all overlays and the underlay $($see red dotted lines$).$

ESXi is currently in Bridge Mode