How can I make an ICS client available to other computers on the host's network?

How can I ping an ICS client from the other computer on the ICS host network? Please see this Diagram of my network.

I would like 'Computer B' to be able to PING the ICS client. Assuming firewalls have been configured properly, how can I address the ICS client from other computers on my network?

ICS HOST ICS CLIENT COMPUTER B
CURRENTLY ICS HOST CAN PING y y y
CURRENTLY ICS CLIENT CAN PING y y y
CURRENTLY COMPUTER B CAN PING y no y

Solution 1:

ICS is very picky. It doesn't support port forwarding aka destination/reverse NAT either, so connecting into the Ethernet network isn't possible.

You should consider using simple routing - activate routing in your current "ICS Host" (disable ICS) and add a static route to the Ethernet network on the Internet router.