I have a VMWare Server installed on my Windows Server.
I just noticed my main switch is 1Gbit but my VMWare Network Adapter VMNet 1 and VMNet8 are both 100Mbit.
Why might that be?
That's just the reported network speed if the virtual network adapter (which is used for either host-only or NAT communications). You can ignore it.
The opposite is often true too from inside the VM. This screenshot I just took is connected to a 1Gbps switch, but the VM shows as connecting at 10Gbps (and guess what, the virtual network adapter on the host says its only 100Mbps).
The fun of virtualisation. You can fake a lot of stuff.
The VMNet host adapter speed is (or should be) cosmetic. The network adapters should be transferring as fast as the Host can handle, assuming the Guest has negotiated properly.
There may, of course, be other factors (such as having a guest fail to negotiate a link) that may reduce speed.