It's especially helpful, being a network engineer (whether design, admin or other) to be able to speak the language of the customers you are dealing with, or at least understand their language enough to make working with them easier. Knowing the basics of DB, VM, MS, etc... can go a long way. You'll find that more people are willing to work with you if you can lean a little in their direction, rather then them having to cater to you. A lot of this comes from experience, but a head start messing around with Apache, MySQL, VMWare and MS applications can provide a great foundation.
That being said, IMO that is true for all fields - if you work in IT you should have a familiarity with the basics across the board. Most applications communicate over a network, a lot deal with databases, have some form of programming, interaction with an OS, etc... The more people on the same page, the better the solution that gets implemented.
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