I specialized in Robotics and AI during my undergraduate coursework in Computer Science. And I heard the same question you received if for a different topic...
"Well we don't do robots...."
"How does Robotics and AI fit into software development?"
I bring this up because the challenge is in selling yourself. First I'm going to give your program the benefit of the doubt and say that your specializing in 'networking' is, rather than the IT focus others are assuming, actually focused on the low level ins and outs of programming for and with network. Specifically this could include security, load balancers, heck even low level socket stuff. There's TONS of ways that networks is a valid and valuable focus during a computer science degree. During my program many students took courses that focused on these topics additionally there was a Masters and PhD program focusing on these topics as part of a Graduate Degree in Computer Science.
That being said. The problem here is selling yourself. Honestly, though few like to admit it, mostly what you're doing while at University, even for CS degrees, is learning how to learn, learning the vocab, getting enough breadth of experience under your belt that you can pick up new things faster and, of course, showing that you can do these things. At the end of the day your specialization(barring specific research done as a PhD candidate which does not sound applicable to your specific situation) is only a way to get slightly more depth in a given field. It's really not something that's going to force you into that specialization. Additionally, in the Software Development Industry, you're going to find a whole SLEW of things that aren't even touched upon during your degree - things that you will learn by working.
What does all of this mean? It means you will get those questions because Managers and Hiring folks are often not familiar with the specific programs at any given educational facility and because, well, CS is still a bit of a wild west when it comes to defining what is useful and what is not. With that in mind, the challenge here is for you to show how what you are learning IS applicable to that company.
"Oh, yes I'm specializing in Networking because I find the low level interactions between systems to be very interesting. However this is just a way to further explore computer science because ..."
A direct example (from my experiences interviewing):
"We don't do robotics here, why would we hire you?"
"Robots are really interesting but they're just a tool for exploring computer science. At the end of the day working with robots is just working with mathematics. I was taking in data and .... blah blah doing programming stuff that was totally related to the company I was interested in"
Switching between specializations is a choice you need to make. But it shouldn't be because someone asked you a question during an interview. You should make a goal to practice explaining why your choices during your education make sense and why they make you valuable. Anyone can learn to program, anyone can bang out some code, anyone can develop software. What makes you different is the choices you make and how you can relate them to the companies you are interested in working for.