You will eventually need to look at something or troubleshoot from the host side. In those cases, you'll usually just install a packet capture tool so you can see what the host is receiving.
For pure network engineering, you're good as long as you know enough to login, install the package, and open the capture viewer. Most places will see some Windows/Linux/Unix skills as a bonus, but host-side issues are entirely the responsibility of system admins in larger organizations.
Being able to fix or investigate issues at the periphery of your role is a great way to stand out. It makes you a natural choice if you want to branch out into new areas (if such opportunities arise). I strongly recommend learning Linux---once you've mastered the material directly related to your job.
Since most Linux distros are free, it is very easy to learn on your own if you have an old PC sitting around. Or you could setup a Linux VM in Hyper-V if you have a newer Windows PC.