Configuring the policy table for default address selection

You can configure the policy table for default address selection to better suit your environment by using the DEFADDRTABLE statement.

Before you begin

Determine whether the default policy table for IPv6 default address selection is appropriate for your environment. If it is not, determine the appropriate policy entries. For more information about the policy table for IPv6 default address selection, including the entries that are in the default table, see Policy table for IPv6 default address selection.

Procedure

Perform the following steps to configure the policy table for default address selection:

Take one of the following actions, depending on how you want to configure the table:
- To configure a new policy table for IPv6 default address selection, add a DEFADDRTABLE block to your TCP/IP profile that contains the appropriate policy entries.
- To change the policy table that is currently being used for IPv6 default address selection, create a DEFADDRTABLE block that contains the existing set of policies (default or configured policies) and update the policy entries that you want to change.
- To remove all policies that are currently configured and revert to the default entries, create a DEFADDRTABLE block that does not contain any policies:
```
DEFADDRTABLE
ENDDEFADDRTABLE
```
Issue the VARY TCPIP,,OBEYFILE command to replace the existing or default policy entries and to activate the configuration changes.

Example

To prefer IPv4 addresses over IPv6 addresses, you can change the precedence of the ::ffff:0.0.0.0/96 prefix to 100. This precedence value gives the IPv4-mapped IPv6 prefix (::ffff:0.0.0.0/96) a higher precedence than all IPv6 prefixes.

DEFADDRTABLE
; Prefix              Precedence  Label
  ::1/128             50          0
  ::/0                40          1
  2002::/16           30          2
  ::/96               20          3
  ::ffff:0.0.0.0/96   100         4
ENDDEFADDRTABLE

To sort global destinations before link-local destinations, you can add an entry to the table for the fe80::/10 prefix. This entry gives link-local destinations (which match the fe80::/10 prefix) a lower precedence than all global addresses (which match the ::/0 prefix).

DEFADDRTABLE
; Prefix              Precedence  Label
  ::1/128             50          0
  ::/0                40          1
  fe80::/10           33          1
  2002::/16           30          2
  ::/96               20          3
  ::ffff:0.0.0.0/96   100         4
ENDDEFADDRTABLE

For information about the DEFADDRTABLE statement, see z/OS Communications Server: IP Configuration Reference.

What to do next

After you have configured the policy table for default address selection, you can display the configured values by issuing the Netstat DEFADDRT/-l command. See Displaying the policy table for default address selection for more information.