I liked learning about raspberry pi and making my own server. I felt like I achieved something cool.
I liked Dijkstra's algorithm myself.
Create a client-server
I think realizing how many layers are actually involved in Networking. It is a lot more complex than I assumed.
I enjoyed learning about the different layers like the application layer or the transport layer.
The labs were really good for this class. Creating a server and a client and being able to send messages and receive messages were really cool.
Also, the Packet Analyzer Lab was really interesting as well with Wireshark. It was also interesting to see how easily what you are browsing can be captured by someone.
Most (important) web traffic uses HTTPS these days, so... even if you capture, it's encrypted and you won't know what information was being sent...