    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  access control
           tables.  These tables are usually in  dbm  or  db  format.
           Alternatively,  access  control tables can be specified in
           CIDR (Classless Inter-Domain Routing) form.

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

           To   test  lookup  tables,  use  the  postmap  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 address.

           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  logi-
                  cal line.

    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

    AUTHOR(S)
           The CIDR table lookup code was originally written by:
           Jozsef Kadlecsik
           kadlec@blackhole.kfki.hu
           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

                                                        CIDR_TABLE(5)