I usually say something like "What happens if I type 'example.com' in my browser's address bar and hit enter?" If someone goes wildly off-track and starts talk

I usually say something like "What happens if I type 'example.com' in my browser's address bar and hit enter?" If someone goes wildly off-track and starts talking about the design of the mechanical switches in the keyboard or I am specifically interested in one area vs another then you can easily tailor it "Ok cool - lets skip ahead to the network aspects" or "lets say I've found the server and downloaded the HTML - now what?" etc. That said, I often like to let people just talk in interviews unless I am really specifically trying to drill into one area and get specific evidence of specific skills. I might jump in with a "Ah - interesting. Tell me more about DNS" or whatever, but usually I find that the good candidates will have a lot to say, and the less-good candidates either say hardly anything, bullshit, or talk a lot but are not good communicators (confusing explanations/hand-waving/etc) ... or a combination of those things :)