Become superuser on the prospective multihomed host.
Create an /etc/hostname.interface file for each additional network interface installed in the machine.
Type:
% touch /etc/notrouter
This creates an empty file called /etc/notrouter.
Reboot the machine.
When the machine reboots, the startup script looks for the presence of the /etc/notrouter file. If the file exists, the startup script does not run in.routed -s or in.rdisc -r, and does not turn on IP forwarding on all interfaces configured "up" by ifconfig. This happens regardless of whether an /etc/gateways file exists. Thus the machine is now a multihomed host.