different networks, same computer (map mapping ?)

["H. S." <greatexcalibur@yahoo.com>]

I would like a laptop to work in two kinds of networks automatically if 
possible. At home, I am running a DHCP server and if the laptop is 
connected to my switch(CAT5 cable to eth0) and booted up, it looks for 
and gets an IP address (it is running a dhcp client). Now when that 
laptop is taken to the university, the user needs to change the 
/etc/network/interfaces file to give the machine a static address. I am 
looking for a way that this choice between dhcp/static happens 
automatically.

I have been reading manpages of interfaces and learned we can map a 
physical device as logical devices and make it work in different modes. 
I am looking for examples where this is already done, the documentation 
in man interfaces is, well,  not very clear about all the nuts and 
bolts, or so I believe. All help is appreciated.

Thanks,
->HS