Internet Protocol version 6 (IPv6) is the latest version of the Internet Protocol (IP), the communications protocol that provides an identification and location system for computers on networks and routes traffic across the Internet. Although its use is not yet widespread, most computer systems already have the capability and the Pi is no different. My own need for it is because I use my work laptop to communicate with both work and home networks. The Junos VPN software permits IPv4 traffic to go to my work network but permits IPv6 traffic to go to my home network. I have no idea whether this is intentional, coincidental or inadvertent.
IPv6 is disabled by default in Raspian but you can easily enable it by adding ipv6 to the file /etc/modules so that IPv6 is loaded at boot time.
At the Pi command line, enter the following command.
sudo nano /etc/modules
Add ipv6 on a new line and save your changes. Reboot and you are finished. You can check that IPv6 is operational by using ifconfig.
This screenshot shows the standard output from ifconfig with the standard IPv4 address, broadcast address and subnet mask for eth0.
The next screenshot shows the output from ifconfig when IPv6 is operational. The highlighted lines show the additional information; first the 128-bit address followed by the size of the network address as a decimal number of bits and the scope in which the address is valid. The loopback interface also has a special IPv6 address assigned.