I have just gone to add a serial connection from my APC UPS to my management server which is running under on a VM on ESXi.
I powered down the VM and then went to add a serial port.
Only to be presented with the ‘Use physical serial port on the host’ Serial Port Output option greyed out.
This is also true when trying to add a pass-through parallel port.
After a quick bit of hunting around it would appear that the serial and parallel port pass-through functionality is not yet enabled in VMware ESXi. It’s not a licensing issue either as my instance of ESXi is licensed.
I know that this is probably a case of RTFM but I thought this worth a quick blog post as others are bound to fall into this same trap.