Edit /etc/rc.conf
The primary IP of the machine will be defined by a line that looks similar to this:
ifconfig_rl0=”inet 192.168.1.2 netmask 255.255.255.0″
To add additional IPs you simply:
ifconfig_rl0_alias0=”inet 192.168.1.3 netmask 255.255.255.255″
ifconfig_rl0_alias1=”inet 192.168.1.4 netmask 255.255.255.255″
