I've been using VirtualBox, and GNS3 for a while and recently I found out about Cisco Packet Tracer.
https://en.wikipedia.org/wiki/Packet_Tracer
I've downloaded it and it seems like this tool is focusing more into Cisco Networking.
The good things about this tool is I can run a lot of guests (pcs, routers, switches) and memory utilization is still very low. Not like GNS3 & VirtualBox.
My question is, can I run actual Linux OS in this packet tracer as I can run it on VirtualBox and GNS3?
Packet tracer is fairly limited. It is designed to let someone practice for the CCNA exams. It doesn't include all the IOS features, only a subset of commands that are useful for CCNA-level exercises.
Packet Tracer is not going to give you what you seem to want.
Packet tracer is a simulator unlike GNS3 which is an emulator. so you cant run linux guest os in packet tracer
You should look into Cisco VIRL. Much more options and seems to be Cisco’s roadmap for emulation instead of packet tracer.
