Under most instances, you do not need to change the IPv6 default address selection policy table. If you do need to administer the policy table, you use the ipaddrsel command.
You might want to modify the policy table under the following circumstances:
If the system has an interface that is used for a 6to4 tunnel, you can give higher priority to 6to4 addresses.
If you want a particular source address to be used only in communications with a particular destination address, you can add these addresses to the policy table. Then, you can use ifconfig to flag these addresses as preferred.
If you want IPv4 addresses to take precedence over IPv6 addresses, you can change the priority of ::ffff:0:0/96 to a higher number.
If you need to assign a higher priority to deprecated addresses, you can add the deprecated address to the policy table. For example, site-local addresses are now deprecated in IPv6. These addresses have the prefix fec0::/10. You can change the policy table to give higher priority to site-local addresses.
For details about the ipaddrsel command, refer to the ipaddrsel(1M) man page.