Problem with IP address


After installing OSX10.1 I can no more connect my mac to a pc.
I use a server (jServe) installed on the mac. It tryes to set up a listener to IP= on Port=21, but an exception occurs telling that it can't assign the requested address.
On Network SystemPreference i've ad IP address, but if i try "ping" it results in a 100% packet loss.
It seems that, regardless of what i set in Network SystemPreferences, i can ping only
Any idea?
I resolved with! I've not realized that I need connect with the network cable an active PC to enable the IP defined in Network Preference.
I don't remember if OSX10.0.4 worked in this way. There is a way to disable this automatic feature and make always enabled my Network Preference IP?
Because in this way i can't leave active the server on the Mac when other PC are down, I need to restart the server on the Mac after at least a pc makes active.