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

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

                                                                                    CIDR_TABLE(5)