ipaddrsel Command

The ipaddrsel command enables you to modify the IPv6 default address selection policy table.

The Oracle Solaris kernel uses the IPv6 default address selection policy table to perform destination address ordering and source address selection for an IPv6 packet header. The /etc/inet/ipaddrsel.conf file contains the policy table.

The following table lists the default address formats and their priorities for the policy table. You can find technical details for IPv6 address selection in the inet6(7P) man page.

Table 11–5 IPv6 Address Selection Policy Table

Prefix	Precedence	Definition
::1/128	50	Loopback
::/0	40	Default
2002::/16	30	6to4
::/96	20	IPv4 Compatible
::ffff:0:0/96	10	IPv4

In this table, IPv6 prefixes (::1/128 and ::/0) take precedence over 6to4 addresses (2002::/16) and IPv4 addresses (::/96 and ::ffff:0:0/96). Therefore, by default, the kernel selects the global IPv6 address of the interface for packets going to another IPv6 destination. The IPv4 address of the interface has a lower priority, particularly for packets going to an IPv6 destination. Given the selected IPv6 source address, the kernel also uses the IPv6 format for the destination address.

Reasons for Modifying the IPv6 Address Selection Policy Table

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.