Q. How to create an internal port group and for what purpose?

Ans:

Go to Host -> configuration -> networking -> adding N/W on the right hand side -> without selecting any IP,VLAN ID, NIC Card through to it because it is for only internal purpose for the communication b/w one to another virtual machine connected through this internal port group. This is highly isolated.

Note: Generally we provide multiple uplinks or physical NIC’s through a VSS for redundancy purose or for load balancing.