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 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:

       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 PATTERN
              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 PATTERN
              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 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.

       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-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.

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_address 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 support is available in Postfix 2.2 and later.

       Before comparisons are made, lookup keys and table entries are
       converted from string to binary. 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.

INLINE SPECIFICATION
       The contents of a table may be specified in the table name (Postfix 3.7
       and later).  The basic syntax is:

       main.cf:
           parameter = .. cidr:{ { rule-1 }, { rule-2 } .. } ..

       master.cf:
           .. -o { parameter = .. cidr:{ { rule-1 }, { rule-2 } .. } .. } ..

       Postfix ignores whitespace after '{' and before '}', and writes each
       rule as one text line to an in-memory file:

       in-memory file:
           rule-1
           rule-2
           ..

       Postfix parses the result as if it is a file in /etc/postfix.

       Note: if a rule contains $, specify $$ to keep Postfix from trying to
       do $name expansion as it evaluates a parameter value.

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)