In the stateful mode, an IPv6 interface is configured through the options in the /etc/rc.conf file. For example, assuming that the IPv6 interface is fxp0 and the IPv6 address is 2001:648:2:220, the configuration file should like as follows:

ipv6_enable="YES"
ipv6_network_interfaces="fxp0"
ipv6_prefix_fxp0="2001:648:2:220"
ipv6_ifconfig_fxp0="2001:648:220::1 prefixlen 64"
ipv6_defaultrouter="2001:648:220::0"
ipv6_prefix_fxp0="3ffe:2d00:2:220"
ipv6_ifconfig_fxp0="3ffe:2d00:220::1 prefixlen 64"
ipv6_default_interface="fxp0"

Linux

Enabling IPv6 in the Linux kernel requires to either recompile the kernel with IPv6 support or to compile/load an appropriate module (without recompiling the whole kernel). Most Linux distributions provide such a module with their precompiled kernels.

The IPv6 module is loaded by using the “modprobe” command, e.g. modprobe ipv6, or by adding an appropriate line to the module configuration file like /etc/modules.conf.

IPv6 stateless address autoconfiguration is the default, so as soon as the module is loaded, IPv6 ad-dresses and appropriate routes should be configured for all interfaces, if router advertisements are present.