install doubt

[Antonello Facchetti]

I'm installing edubuntu 6.06 as an ltsp server.
The pc has got two nics, one for the terminals and the other to access 
to the internet.
The installaton procedure asks to configure the so-called "main ethernet 
card", but I can't figure out which one of the nics is the "main" nic: 
is it the one for the thin clients or the one to access the internet?
I could find no hint in the documentation.

tia
Antonello