wikipedia.org:
https://en.wikipedia.org/wiki/IPv6

Internet Protocol version 6 (IPv6):
Testing both for IPv4 and IPv6: www.workingornot.org/.
This tool by me works with a proxy server.

Eg setup for a VPS:
IPv6 address such as 2a01:7c8:d008:32:5054:ff:fee8:665a
The gateway address ends with 1, such as 2a01: 7c8: d008 :: 1.

• AAAA, quad A, is always preferred over A;
  The application server can be limited to IPv4 (can come to a dead end);
• Value, eg using ODBC, between brackets such as [2a01:7c8:aab1:282::1].
  (I do stabilize ODBC with an IPv4 address instead of a domain name)

Find out the IPv6 address:
$ ip -6 addr show

A firewall may block:
In case of non-standard SSH port, open for IPv6 as well.

The IPv6 address of the internet connection can change e.g. every 15 minutes:
Stabilize programming code in case of a security login check .