whitepaper - understanding IP addresses
http://pages.di.unipi.it/ricci/501302.pdf

80|LXF200 - IPv6

IPv6 disabling
https://www.blackmoreops.com/2015/08/04/how-to-disable-ipv6-in-linux/
/etc/gai.conf
precedence ::ffff:0:0/96  100