Don’t ask me why – but Apple decided to move the Network Utility app in OSX Mavericks. I use it all the time when troubleshooting networks for clients. It’s handy and does the basic job well.
It’s now located in the following directory / folder:
/System/Library/CoreServices/Applications/
Previously it was in the /applications/utilities folder. Why Apple moved it is beyond me.
It should still show up in Spotlight, but in case it doesn’t I’d suggest making an alias to it and put it on the dock or desktop.
If you want to know how to do this, contact me or comment and I will build a video for it.