This is how to setup a virtual interface on Slackware:
/etc/rc.d/rc.inet1.conf
## Virtual Interfaces # eth0:1 vif IFNAME[4]="eth0:1" IPADDR[4]="192.168.1.2" NETMASK[4]="255.255.255.0" USE_DHCP[4]="no" DHCP_HOSTNAME[4]="" # eth0:2 vif IFNAME[5]="eth0:2" IPADDR[5]="192.168.1.3" NETMASK[5]="255.255.255.0" USE_DHCP[5]="no" DHCP_HOSTNAME[5]=""
rc.inet1
, or manually restart each vif