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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.  Alterna‐
       tively, 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 ":".

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

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)