Found that for some reason INSTALL had not detected my old NIC, (3com 3c509c), and had not created an rc.netdevice file
Searched in the SlackWare documentation and found some good advice on editing the rc.modules
file. Modified as suggested, rebooted and now on-line.
Ref to manual page:
section 5.2.1 in http://www.slackbook.org/html/networ...-hardware.html