The problem you have had with the Puppy Network Wizard + rc.network, is not a limitation of the IP software, but rather it seems to be a limitation of the wizard and rc.network. It assumes that both interfaces need to be configured, and/or brought up, at the same time. Okay. That would explain the ...

I would be surprised if you had any problems with the wizard and/or dhcp, if you only plugged in only one of the devices at a time. Good point. But I have been doing some more tweaking. I can now move back and forth from DCHP to static routing in real time without rebooting and without any SCIOADDR...

I have two network interfaces, one wireless (wlan0, 192.168.1.15) and one ethernet (eth0, 192.168.1.14). It was my intention to use eth0 for a LAN and wlan0 (connected to my wireless router which is 192.168.1.1) for the internet, using static ip addresses. I think my problem was very similar to you...