Manual Pages for UNIX Operating System command usage for man ipaddrsel

System Administration Commands                      ipaddrsel(1M)



NAME
     ipaddrsel - configure IPv6 default address selection

SYNOPSIS
     /usr/sbin/ipaddrsel


     /usr/sbin/ipaddrsel -f file


     /usr/sbin/ipaddrsel -d


DESCRIPTION
     Use the ipaddrsel utility  to  configure  the  IPv6  default
     address  selection  policy  table.  The  policy  table  is a
     longest-matching-prefix lookup table that is used  for  IPv6
     source  address selection and for destination address order-
     ing when  resolving  names  to  AF_INET6  addresses.  For  a
     description  of  how  the  policy  table  is used for source
     address selection, see inet6(7P). For a description  of  how
     the  policy  table is used for destination address ordering,
     see getaddrinfo(3SOCKET).


     The unmodified policy table is valid for  all  typical  IPv6
     deployments.  Modify the table only if a circumstance exists
     for which the default behavior of the  IPv6  source  address
     selection or destination address ordering mechanism is unsa-
     tisfactory. See the   section  for  examples  of  such  cir-
     cumstances.  You  should  carefully consider your addressing
     strategy before you  change  the  table  from  the  provided
     default.


     When the ipaddrsel command is issued without any  arguments,
     the  address  selection  policy currently in use is printed.
     The format of the output is compatible with  the  format  of
     the configuration file that the -f option accepts.

     Note -

       If the usesrc subcommand to ifconfig(1M) is applied  to  a
       particular physical interface, the selection policy speci-
       fied by usesrc overrides the source address selection pol-
       icies  specified  by  ipaddrsel.  This is true for packets
       that are locally generated and for  applications  that  do
       not choose a non-zero source address using bind(3SOCKET).

  The Configuration File
     The configuration file that the -f option accepts  can  con-
     tain  either  comment lines or policy entries. Comment lines



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System Administration Commands                      ipaddrsel(1M)



     have a '#' character as the first non-blank  character.  and
     they  are  ignored  by  the  ipaddrsel utility. Policy entry
     lines have the following format:

       prefix/prefix_length precedence label [# comment]



     The prefix must be an IPv6 prefix  in  a  format  consistent
     with  inet(3SOCKET). The prefix_length is an integer ranging
     from 0 to 128. The IPv6 source address selection and  desti-
     nation  address ordering algorithms determine the precedence
     or label of  an  address  by  doing  a  longest-prefix-match
     lookup  using the prefixes in this table, much like next-hop
     determination for a destination is done by doing a  longest-
     prefix-match lookup using an IP routing table.


     The precedence is a non-negative integer that represents how
     the   destination   address  ordering  mechanism  will  sort
     addresses returned from name lookups. In general,  addresses
     with  a higher precedence will be in front of addresses with
     a lower precedence. Other factors, such as destinations with
     undesirable  source  addresses  can, however, override these
     precedence values.


     The label is a string of at  most  fifteen  characters,  not
     including  the  NULL terminator. The label allows particular
     source address prefixes to be used with destination prefixes
     of  the  same label. Specifically, for a particular destina-
     tion address, the IPv6 source  address  selection  algorithm
     prefers  source  addresses  whose label is equal that of the
     destination.


     The label may be followed by an optional comment.


     The file must contain a default policy entry,  which  is  an
     entry with ::0/0 as its prefix and prefix_length. This is to
     ensure that all possible addresses match a policy.

OPTIONS
     The ippadrsel utility supports the following options:

     -f file    Replace the address selection policy  table  with
                the policy specified in the file.


     -d         Revert  the  kernel's  address  selection  policy
                table   back   to  the  default  table.  Invoking



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System Administration Commands                      ipaddrsel(1M)



                ipaddrsel in this way only changes the  currently
                running kernel's policy table, and does not alter
                the configuration file  /etc/inet/ipaddrsel.conf.
                To  revert  the  configuration  file  back to its
                default settings, use ipaddrsel -d, then dump the
                contents  of  the table to the configuration file
                by  redirecting  the  output  of   ipaddrsel   to
                /etc/inet/ipaddrsel.conf.

                  example# ipaddrsel -d
                  example# ipaddrsel > /etc/inet/ipaddrsel.conf




EXAMPLES
     Example 1 The Default Policy in /etc/inet/ipaddrsel.conf


     The following example is the default policy that is  located
     in /etc/inet/ipaddrsel.conf:


       # Prefix                            Precedence Label
       ::1/128                             50 Loopback
       ::/96                               20 IPv4_Compatible
       ::ffff:0.0.0.0/96                   10 IPv4
       2002::/16                           30 6to4
       ::/0                                40 Default



     Example 2 Assigning a Lower  Precedence  to  Link-local  and
     Site-local Addresses


     By default, the  destination  address  ordering  rules  sort
     addresses of smaller scope before those of larger scope. For
     example, if a name resolves to a  global  and  a  site-local
     address,  the site local address would be ordered before the
     global address. An administrator can override this  ordering
     rule by assigning a lower precedence to addresses of smaller
     scope, as the following table demonstrates.


       # Prefix                             Precedence Label
       ::1/128                              50 Loopback
       ::/0                                 40 Default
       2002::/16                            30 6to4
       fec0::/10                            27 Site-Local
       fe80::/10                            23 Link-Local
       ::/96                                20 IPv4_Compatible



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System Administration Commands                      ipaddrsel(1M)



       ::ffff:0.0.0.0/96                    10 IPv4



     Example 3 Assigning Higher Precedence to IPv4 Destinations


     By default, IPv6 addresses are  ordered  in  front  of  IPv4
     addresses  in name lookups. ::ffff:0.0.0.0/96 has the lowest
     precedence in the default table. In the  following  example,
     IPv4  addresses  are  assigned  higher  precedence  and  are
     ordered in front of IPv6 destinations:


       # Prefix                             Precedence Label
       ::1/128                              50 Loopback
       ::/0                                 40 Default
       2002::/16                            30 6to4
       ::/96                                20 IPv4_Compatible
       ::ffff:0.0.0.0/96                    60 IPv4



     Example 4 Ensuring that a Particular Source Address is Used


     This example ensures that a  particular  source  address  is
     used only when communicating with destinations in a particu-
     lar network.



     The following policy table assigns a label of 5 to a partic-
     ular  source address on the local system, 2001:1111:1111::1.
     The  table  assigns   the   same   label   to   a   network,
     2001:2222:2222::/48.  The  result of this policy is that the
     2001:1111:1111::1 source address will only be used when com-
     municating    with    destinations    contained    in    the
     2001:2222:2222::/48 network. For this example, this  network
     is   the  ClientNet,  which  could  represent  a  particular
     client's network.


       # Prefix                              Precedence Label
       ::1/128                               50 Loopback
       2001:1111:1111::1/128                 40 ClientNet
       2001:2222:2222::/48                   40 ClientNet
       ::/0                                  40 Default
       2002::/16                             30 6to4
       ::/96                                 20 IPv4_Compatible
       ::ffff:0.0.0.0/96                     10 IPv4




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System Administration Commands                      ipaddrsel(1M)



     This example assumes that the local system has one  physical
     interface, and that all global prefixes are assigned to that
     physical interface.


EXIT STATUS
     ipaddrsel returns the following exit values:

     0     ipaddrsel successfully completed.


     >0    An error occurred. If a failure  is  encountered,  the
           kernel's current policy table is unchanged.


FILES
     /etc/inet/ipaddrsel.conf    The file that contains the  IPv6
                                 default address selection policy
                                 to be installed  at  boot  time.
                                 This  file  is loaded before any
                                 Internet services are started.


ATTRIBUTES
     See attributes(5) for descriptions of the  following  attri-
     butes:



     ____________________________________________________________
    |       ATTRIBUTE TYPE        |       ATTRIBUTE VALUE       |
    |_____________________________|_____________________________|
    | Availability                | SUNWcs                      |
    |_____________________________|_____________________________|
    | Interface Stability         | Committed                   |
    |_____________________________|_____________________________|


SEE ALSO
     nscd(1M),        inet(3SOCKET),        getaddrinfo(3SOCKET),
     ipaddrsel.conf(4), attributes(5), inet6(7P)

NOTES
     The ipnodes cache kept by nscd(1M) contains  addresses  that
     are  ordered  using  the  destination address ordering algo-
     rithm, which is one of the reasons why ipaddrsel  is  called
     before  nscd  in  the boot sequence. If ipaddrsel is used to
     change the address selection policy after nscd has  started,
     you  should invalidate the nscd ipnodes cache invalidated by
     invoking the following command:

       example# /usr/sbin/nscd -i ipnodes



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System Administration Commands                      ipaddrsel(1M)























































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