Ask HN: Resources for learning Networking?

I feel like I understand a fair bit about networking, but the more I learn the more I realize I know very little. A few months ago I wrote a bit of the code in Docker that sets up a container's route table in an effort to teach myself more, but I'm not entirely sure where to go from here to keep learning.

What are some good resources around networking that you've found helpful? Should I just keep exploring man pages? Are there better and more directed resources out there you've used to go from clueless to dangerous?

Thanks!