interview questions?

What are you interviewing for?  A technician?  An Admin?  A programmer?  what?

The questions you ask should be dependent upon the products.  PRESUMABLY you know the technology... so ask them about the technology.  Give them scenarios and ask them how they would deal with the issue?  

Things like:
When setting up a LAN, how do you like to handle IP addressing?  Device Names?  What's you're ideal WAN configuration?  What about when you only have $X per month for connectiivty but also have y requirements?  What are some VOIP best practices?  When you setup a file server, how to you prefer to setup permissions?  etc. PRESUMABLY you have policies and understanding of these things and will know what kind of answer you want to hear.  If you're smart, you're also looking for other perspectives and if they give you one you don't do or don't know, you'll followup on why they think that's best... if you agree that it is correct BUT you know you have reasons you don't always do that, ask them how they'd handle the situation when x requires y?   You are testing them, but you're NOT giving them multiple choice or grading... it's a conversation to understant their technical skill compared to yours and how they can benefit the company and if they are a team player who will also benefit YOU.  (YOU are not the primary reason they are there - but if they aren't a team player, you won't benefit AND the company will likely suffer with lower productivity and potentially personality conflicts.

Are you one of the Interviewers?   If so, sit with one of your colleagues and determine what the hot buttons are for each of the technologies you posted.  The total of the list above is huge in scope.

You need to be able to ask one or two key questions for each item in the list and that will depend on what you are doing in your shops