    CIDR_TABLE(5)                                                    CIDR_TABLE(5)

    NAME
           cidr_table - format of Postfix CIDR tables

    SYNOPSIS
           postmap -q "string" cidr:/etc/postfix/filename

           postmap -q - cidr:/etc/postfix/filename <inputfile

    DESCRIPTION
           The  Postfix mail system uses optional lookup tables.  These tables are
           usually in dbm or db format.  Alternatively, lookup tables can be spec-
           ified in CIDR (Classless Inter-Domain Routing) form. In this case, each
           input is compared against a list of patterns. When a  match  is  found,
           the corresponding result is returned and the search is terminated.

           To  find  out  what types of lookup tables your Postfix system supports
           use the "postconf -m" command.

           To test lookup tables, use the "postmap -q" command as described in the
           SYNOPSIS above.

    TABLE FORMAT
           The general form of a Postfix CIDR table is:

           network_address/network_mask     result
                  When  a  search  string matches the specified network block, use
                  the corresponding result value. Specify 0.0.0.0/0 to match every
                  IPv4 address, and ::/0 to match every IPv6 address.

                  An  IPv4  network  address  is a sequence of four decimal octets
                  separated by ".", and an IPv6 network address is a  sequence  of
                  three to eight hexadecimal octet pairs separated by ":".

                  The  network_mask  is  the number of high-order bits in the net-
                  work_address that the search string must match.

                  Before comparisons are made, lookup keys and table  entries  are
                  converted from string to binary. Therefore table entries will be
                  matched regardless of redundant zero characters.

                  Note: address information may be enclosed inside "[]"  but  this
                  form is not required.

                  IPv6 support is available in Postfix 2.2 and later.

           network_address     result
                  When  a search string matches the specified network address, use
                  the corresponding result value.

           blank lines and comments
                  Empty lines and whitespace-only lines are ignored, as are  lines
                  whose first non-whitespace character is a `#'.

           multi-line text
                  A  logical  line  starts  with  non-whitespace text. A line that
                  starts with whitespace continues a logical line.

    TABLE SEARCH ORDER
           Patterns are applied in the order as specified in the  table,  until  a
           pattern is found that matches the search string.

    EXAMPLE SMTPD ACCESS MAP
           /etc/postfix/main.cf:
               smtpd_client_restrictions = ... cidr:/etc/postfix/client.cidr ...

           /etc/postfix/client.cidr:
               # Rule order matters. Put more specific whitelist entries
               # before more general blacklist entries.
               192.168.1.1             OK
               192.168.0.0/16          REJECT

    SEE ALSO
           postmap(1), Postfix lookup table manager
           regexp_table(5), format of regular expression tables
           pcre_table(5), format of PCRE tables

    README FILES
           DATABASE_README, Postfix lookup table overview

    HISTORY
           CIDR table support was introduced with Postfix version 2.1.

    AUTHOR(S)
           The CIDR table lookup code was originally written by:
           Jozsef Kadlecsik
           KFKI Research Institute for Particle and Nuclear Physics
           POB. 49
           1525 Budapest, Hungary

           Adopted and adapted by:
           Wietse Venema
           IBM T.J. Watson Research
           P.O. Box 704
           Yorktown Heights, NY 10598, USA

           Wietse Venema
           Google, Inc.
           111 8th Avenue
           New York, NY 10011, USA

                                                                     CIDR_TABLE(5)