How you would do it depends on your hardware setup and the configuration requirements of your sharing software. It's also a default gateway issue. I used to have this sort of setup with mine and my wife's computers using NAT32 as the sharing software - the first computer to connect would share the connection with the late-comer, with no tcp/ip reconfiguration required. It was possible with NAT32 because the LAN NICs could have static IP addresses in the 192.168.0.X private range, and NAT32's virtual IP address could be different on each computer (eg. 192.168.0.100 on one, and 192.168.0.101 on the other), with each computer's LAN NIC's gateway set at the NAT32 virtual IP address of the other computer, with the same settings working for either server and client roles. Other NAT software might not be as flexible.