SL4P default setup

The Network Manager, well, manages the connections, and ask for an IP address through a DHCP request.
You can set it up through a right-click on the Xfce desktop icon.
It's not included in the stock Slackware.

Slackware friendly setup

Wicd is included in the stock Slackware extra packages, and i shipped it in SL4P.
I tried it only a bit so i can't recommend it, or not.
If you want to give it a try, be root, then disable the network manager. Edit /etc/rc.d/rc.local and comment at the end:

/etc/rc.d/rc.networkmanager start

into

#/etc/rc.d/rc.networkmanager start

chmod +x /etc/rc.d/rc.wicd

Activate Wicd frontend under Xfce. Go in the menu -> Settings -> Session and Startup -> Application Autostart tab, then check "Wicd Network Manager Tray".
Reboot.

Stock Slackware doesn't use the Network Manager, nor Wicd. The network is established at boot, once for all.
If you want a non-graphical server-oriented setup, you have to disable the network manager (and Wicd). Edit /etc/rc.d/rc.local and comment at the end:

/etc/rc.d/rc.networkmanager start

into

#/etc/rc.d/rc.networkmanager start

netconfig

darkstar

otherwise you'll break some Pandora scripts compatibility. Sudo won't launch anything with the wrong hostname.

Set you parameters.
Edit /etc/rc.d/rc.inet1.conf to finalize your setup.
Be sure to have all used interfaces plugged in when booting. With the deactivation of the network manager, it's no more plug and play.