dhcpcd will have to be run somehow, every time the computer reboots. If you don't want to do this manually (that'd get old quickly) you can try to use the Slackware network configuration tool. (As root, run netconfig)
If that doesn't work for any reason, you can make dhcpcd run automatically by adding the line "dhcpcd" to the end of /etc/rc.d/rc.local. You can do that, as root, with:
Code:
echo "dhcpcd" >> /etc/rc.d/rc.local
The prefered way would be to use netconfig, though.