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 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 ":".

  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

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    /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