Where to Find Answer to Technical Questions

First of all, read

◇ How To Ask Questions The Smart Way

Stack Exchange Sites

◇ https://serverfault.com/
◇ https://unix.stackexchange.com/
◇ https://stackoverflow.com/

RFC

s
◇ https://www.ietf.org/
◇ http://www.faqs.org/rfcs/

Manpages

◇ https://www.kernel.org/doc/man-pages/
◇ https://linux.die.net/man/

Books

◇ Networking for System Administrators by Michael Lucas
▪ Official Site