I believe that IPv4 is a fundamental to the profession of information technology, information security, and cyber security.

To call IPv4 an outdated technology and ignore learning the fundamentals, how to calculate subnets, and the roles of the interconnected networking devices as they relate to the TCP/IP stack would not be wise since everything is increasingly interconnected every day.

https://en.wikipedia.org/wiki/Internet_protocol_suite

Helpful Links:

Visual Subnet Calculator: www.cidr.xyz

Cisco Developer Sandbox: https://developer.cisco.com/site/sandbox/

Global internet connected devices search engine: https://www.shodan.io/

Free SSL Certificates: https://letsencrypt.org/

SANS Internet Storm Center: https://dshield.org/