You're talking about ifconfig on a real computer, right?

That's very well, but what about the other machines on the network? I don't see how I can take a private address I've been assigned for my home network and legitimately use it on our work network. Doesn't it defeat the point of address allocation if people effectively make up addresses? I think I'd be in trouble if I caused a conflict. (Did I ever mention the guy who mistyped an IP address when configuring his new machine, so that it stole traffic for the router and then dropped it all? Not very popular!)

Anyway, my real aim was the one about ntpdate; I thought I was making my question simpler by asking about addresses - now I've learnt a lesson!