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CIDR_TABLE(5)                            File Formats Manual                           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 specified in CIDR (Classless Inter-Domain  Rout‐
       ing)  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:

       pattern     result
              When  a  search  string  matches  the  specified pattern, use the corresponding result
              value. The pattern must be in network/prefix or network_address form (see ADDRESS PAT‐
              TERN SYNTAX below).

       !pattern     result
              When  a  search  string does not match the specified pattern, use the specified result
              value. The pattern must be in network/prefix or network_address form (see ADDRESS PAT‐
              TERN SYNTAX below).

              This feature is available in Postfix 3.2 and later.

       if pattern

       endif  When  a  search string matches the specified pattern, match that search string against
              the patterns between if and endif.  The pattern must  be  in  network/prefix  or  net‐
              work_address form (see ADDRESS PATTERN SYNTAX below). The if..endif can nest.

              Note: do not prepend whitespace to text between if..endif.

              This feature is available in Postfix 3.2 and later.

       if !pattern

       endif  When  a  search  string does not match the specified pattern, match that search string
              against the patterns between if and endif. The pattern must be  in  network/prefix  or
              network_address form (see ADDRESS PATTERN SYNTAX below). The if..endif can nest.

              Note: do not prepend whitespace to text between if..endif.

              This feature is available in Postfix 3.2 and later.

       blank lines and comments
              Empty lines and whitespace-only lines are ignored, as are lines whose first non-white‐
              space 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.

ADDRESS PATTERN SYNTAX
       Postfix CIDR tables are pattern-based. A pattern is either a network_address  which  requires
       an exact match, or a network_address/prefix_length where the prefix_length part specifies the
       length of the network_address prefix that must be matched (the other bits in the  network_ad‐
       dress part must be zero).

       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  ":"  or
       "::",  where the latter is short-hand for a sequence of one or more all-zero octet pairs. The
       pattern 0.0.0.0/0 matches every IPv4 address, and ::/0 matches every IPv6 address.  IPv6 sup‐
       port is available in Postfix 2.2 and later.

       Before  comparisons  are made, lookup keys and table entries are converted from string to bi‐
       nary. Therefore, IPv6 patterns will be matched regardless of leading zeros (a leading zero in
       an IPv4 address octet indicates octal notation).

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

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 allowlist entries
           # before more general denylist entries.
           192.168.1.1             OK
           192.168.0.0/16          REJECT
           2001:db8::1             OK
           2001:db8::/32           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

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



                                                                                       CIDR_TABLE(5)