Not often needed, sometimes in cases of dedicated point-to-point links.
Usage:
| # /sbin/ip -6 route add <ipv6network>/<prefixlength> dev <device> ¬ metric 1 | 
Example:
| # /sbin/ip -6 route add default dev eth0 metric 1 | 
Metric “1” is used here to be compatible with the metric used by route, because the default metric on using “ip” is “1024”.
Usage:
| # /sbin/route -A inet6 add <ipv6network>/<prefixlength> dev <device> | 
Example:
| # /sbin/route -A inet6 add default dev eth0 |