VMWare ESXi 6.5a unhandled exception / invalid disk image errors

The default web interface module in the ESXi 6.5a iso release is buggy, get the latest web interface update from this link (direct link to the vib).

Links are borking - here https://labs.vmware.com/flings/esxi-embedded-host-client/

GNS3 + Centos 7.x

This and this (or it doesn't start).

Access VirtualBox guests from host and vice versa

In order to communicate between your VM's and host, add a host-only network adapter on the VM properties.  The IP associated with this adapter will be reachable by the host.