DEFADDRTABLE statement

Use the DEFADDRTABLE statement to configure the policy table for IPv6 default address selection. If you do not configure the policy table for IPv6 default address selection with the DEFADDRTABLE profile statement, then the following default policy table is used:

    Prefix             Precedence Label
    ::1/128            50         0
    ::/0               40         1
    2002::/16          30         2
    ::/96              20         3
    ::ffff:0.0.0.0/96  10         4

Restriction: Only one DEFADDRTABLE block should appear in a configuration data set. Any subsequent DEFADDRTABLE blocks are ignored, and an informational message is displayed. If a syntax error is encountered when this statement is processed, an error message is displayed, and the entire DEFADDRTABLE block is ignored (no entries are processed).

Guideline: The order of the entries in the policy table is not important. When the policy table is used during address selection, all entries in the table are searched to locate the entry with the prefix that best matches (longest prefix match) the address for which precedence and label values are needed.

For more information about the policy table for default address selection and the precedence and label values, see z/OS Communications Server: IPv6 Network and Application Design Guide.

Syntax


                 .------------------.                    
                 V                  |                    
>>-DEFADDRTable----| Policy Entry |-+--ENDDEFADDRTable---------><

Policy Entry

   .-----------------------------------------.   
   V                                         |   
|----prefix/prefix_length--precedence--label-+------------------|

Parameters

prefix/prefix_length

The address prefix that is used to select the policy table entry that best matches a source address or a destination address. The policy table is a longest-matching-prefix lookup table.

If duplicate prefix entries are specified in the same DEFADDRTABLE block, the first prefix entry is used, the remaining duplicate prefix entries are ignored, and messages are displayed.

prefix: The digits (in colon-hexadecimal format) before the slash (/) specify the prefix.
prefix_length: An integer value in the range 0 - 128 that specifies the length of the prefix, in bits.

precedence

An integer value in the range 0 - 65530 that specifies the precedence that is used to sort destination addresses.

label

An integer value in the range 0 - 65530 that specifies that a particular source address prefix is preferred for use with a destination address prefix.

Steps for modifying

The following considerations apply when you modify the DEFADDRTABLE block:

To remove all the current configured policies, specify the DEFADDRTABLE block without any entries:
```
DEFADDRTABLE ENDDEFADDRTABLE
```
Issue the VARY TCPIP,,OBEYFILE command; the default policy table replaces the previously configured values.
To change any of the policy entries, create a DEFADDRTABLE block with the existing set of policies. Update the policy entries that need to be changed. Then, issue the VARY TCPIP,,OBEYFILE command to activate the change. The new policy table completely replaces the existing policy table.

Examples

The default policy table contains the following values:

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

This default table specifies the following behavior:

Prefer using native source addresses with native destination addresses, 6to4 source addresses with 6to4 destination addresses, and IPv4-compatible source addresses with IPv4-compatible destination addresses
Guideline: IPv4-compatible addresses have been deprecated by RFC 4291, but are shown here because they are part of the default policy table defined by RFC 3484.
Prefer using IPv6 network transport over IPv4 network transport when possible

To specify that IPv4 network transport should be preferred over IPv6 network transport, change the precedence of the ::ffff:0.0.0.0/96 prefix to 100.

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

All other considerations being equal, a destination address whose label does not match the label of any of the possible source addresses prefers an IPv4 source address because the precedence value for the ::ffff:0.0.0.0/96 prefix is higher than the precedence value of all the other entries.

The destination address selection rules give preference to destinations of smaller scope. For example, a link-local destination is sorted before a global scope destination when the two are otherwise equally suitable. To sort global destinations before link-local destinations, change the policy table to reverse the existing preference.

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