What I did was study the material for the Comptia Network+ certification. Don't have to take the exam since it's not the most marketable cert, but it'll give you all the fundamental knowledge and concepts! You can find study videos on YouTube or there are plenty of torrents of paid training vids.

Skillsforall.com is free and carries the Cisco logo. You'll want to take "getting started with packet tracer" then "networking basics" followed by "networking devices and initial configuration".

I teach CCNA Introduction to Networking as part of an intro to devops course, and while the courses listed above don't entirely cover the first semester of the CCNA, they do cover about 2/3, and I actually use the packet tracer course.

Unironically, Wikipedia is the best resource - it also points to better resources. If you want networking themed videos, Network Chuck is also a great resource.

Add in Professer Messer for the concepts. He has his own webpage and is on YouTube.

CBT Nuggets is doing great work as always. Subscriptions are quite expensive at $60/mo. but get you a ton of high quality information. You can find a lot of their content online for free as well.