More fun with "my" New Laptop

McKee

That's a very common policy, typically enforced at the network switch level. A typical pro (as opposed to home) switch can be configured to only allow traffic from MAC addresses that are on its list, and can often even be set to shut down any port upon which it detects an unauthorized machine (which can then require some explaining when you have to tell IT why someone was trying to violate company policy in your office...).

George: if you don't actually need to access things on their network while there, but just want to get to the internet, you might ask them if there is a conference room that you could do this from. Many places will have their conference rooms that are used for meetings with outside people on a separate network from their internal LAN, with the conference room providing only outside access, with few restrictions.

-- --Tim Smith