Uhm, yes. So long as A.B.C.X is a public address with a route to it from the internet then its as simple as making sure that packet forwarding is enabled on your firewall using
Code:
echo "1" > /proc/sys/net/ipv4/ip_forward
at boot time. If A.B.C.X isn't a public address that you'd need to use port forwarding on your public interface to just forward specific ports to specific hosts, with IP Masquerading/NAT for outgoing traffic.
HTH
Jamie...