Hermes
CCSDS
Introduction to Telemetry Systems - TTi

Packet Pioneer (Wireshark)
Practical Networking
Practical Networking - CCNA
Jeremy's IT Lab
Packet Life
Learning Tech Training
Cisco CCNA Lab Manual (pdf)
Cisco Command Hierarchy
Jeremy's IT Lab Free CCNA 200-301 (YouTube)
FlackBox

Linux Sec Tools
SourceForge
PicoCTF
Ollydbg Example
highon.coffee

Port Forward
MITRE|ATT&CK
Router Freak

Where Wizards Stay Up Late
TCP Guide
Sam Bowne