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 specified 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 network_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

       Use "postconf readme_directory" or "postconf html_directory" to locate this information.
       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

                                                                                                   CIDR_TABLE(5)