It was a plus when I came from a military network to a public one, I was a lot more security-conscious then. The end users didn't like it at first when I did things like make them change their passwords on a regular basis, but I literally told them there was a new sherrif in town. Play up your security concerns when discussing the network, it's always good!!
If you don't know on a TEHCNICAL issue, tell them that, then demonstrate your assertiveness and resourcefulness by explaining how you would go about getting the answer. Don't try to BS your way through it, as interviewers they always include the answer they are looking for.
And when they get to the question "Do you have any questions to ask us" DO NOT ask about pay, perks, etc. Ask a question that shows you did some research about the company, the products involved, the size of the IT group, just not "how much will I get" or "How soon can I move up"